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	$164.26	6.192%	$174.431	$174.43	$174.45	$174.40
Purchase #2	$85.41	3.252%	$88.1875	$88.19	$88.20	$88.20
Purchase #3	$245.34	11.337%	$273.1542	$273.15	$273.15	$273.20
Purchase #4	$61.72	9.589%	$67.6383	$67.64	$67.65	$67.60
Purchase #5	$50.49	4.285%	$52.6535	$52.65	$52.65	$52.70
Purchase #6	$30.80	10.851%	$34.1421	$34.14	$34.15	$34.10
Purchase #7	$37.83	12.517%	$42.5652	$42.57	$42.55	$42.60
7 purchase totals =	$675.85		$732.7718	$732.77	$732.80	$732.80