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	$206.73	8.759%	$224.8375	$224.84	$224.85	$224.80
Purchase #2	$137.81	9.289%	$150.6112	$150.61	$150.60	$150.60
Purchase #3	$240.48	10.442%	$265.5909	$265.59	$265.60	$265.60
Purchase #4	$105.72	6.517%	$112.6098	$112.61	$112.60	$112.60
Purchase #5	$31.37	9.794%	$34.4424	$34.44	$34.45	$34.40
Purchase #6	$176.98	9.651%	$194.0603	$194.06	$194.05	$194.10
Purchase #7	$55.55	6.444%	$59.1296	$59.13	$59.15	$59.10
7 purchase totals =	$954.64		$1,041.2817	$1,041.28	$1,041.30	$1,041.20