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	$181.81	5.346%	$191.5296	$191.53	$191.55	$191.50
Purchase #2	$160.71	11.834%	$179.7284	$179.73	$179.75	$179.70
Purchase #3	$150.72	11.872%	$168.6135	$168.61	$168.60	$168.60
Purchase #4	$61.65	13.587%	$70.0264	$70.03	$70.05	$70.00
Purchase #5	$76.93	7.346%	$82.5813	$82.58	$82.60	$82.60
Purchase #6	$142.59	11.558%	$159.0706	$159.07	$159.05	$159.10
Purchase #7	$233.99	5.370%	$246.5553	$246.56	$246.55	$246.60
7 purchase totals =	$1,008.40		$1,098.1051	$1,098.11	$1,098.15	$1,098.10