Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.55	9.590%	$185.8098	$185.81	$185.80	$185.80
Purchase #2	$200.62	11.854%	$224.4015	$224.40	$224.40	$224.40
Purchase #3	$94.82	11.334%	$105.5669	$105.57	$105.55	$105.60
Purchase #4	$185.82	5.758%	$196.5195	$196.52	$196.50	$196.50
Purchase #5	$137.29	12.474%	$154.4156	$154.42	$154.40	$154.40
Purchase #6	$98.68	10.515%	$109.0562	$109.06	$109.05	$109.10
Purchase #7	$145.51	3.186%	$150.1459	$150.15	$150.15	$150.10
7 purchase totals =	$1,032.29		$1,125.9154	$1,125.93	$1,125.85	$1,125.90