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	$76.65	8.448%	$83.1254	$83.13	$83.15	$83.10
Purchase #2	$147.70	12.166%	$165.6692	$165.67	$165.65	$165.70
Purchase #3	$216.93	5.280%	$228.3839	$228.38	$228.40	$228.40
Purchase #4	$228.65	3.714%	$237.1421	$237.14	$237.15	$237.10
Purchase #5	$193.72	11.557%	$216.1082	$216.11	$216.10	$216.10
Purchase #6	$85.64	5.261%	$90.1455	$90.15	$90.15	$90.10
Purchase #7	$208.82	6.759%	$222.9341	$222.93	$222.95	$222.90
7 purchase totals =	$1,158.11		$1,243.5084	$1,243.51	$1,243.55	$1,243.40