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	$204.91	9.102%	$223.5609	$223.56	$223.55	$223.60
Purchase #2	$109.88	8.180%	$118.8682	$118.87	$118.85	$118.90
Purchase #3	$190.42	10.872%	$211.1225	$211.12	$211.10	$211.10
Purchase #4	$246.45	6.529%	$262.5407	$262.54	$262.55	$262.50
Purchase #5	$149.76	6.745%	$159.8613	$159.86	$159.85	$159.90
Purchase #6	$229.33	11.685%	$256.1272	$256.13	$256.15	$256.10
Purchase #7	$167.76	13.228%	$189.9513	$189.95	$189.95	$190.00
7 purchase totals =	$1,298.51		$1,422.0321	$1,422.03	$1,422.00	$1,422.10