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	$236.29	13.518%	$268.2317	$268.23	$268.25	$268.20
Purchase #2	$57.32	4.248%	$59.755	$59.76	$59.75	$59.80
Purchase #3	$78.60	6.431%	$83.6548	$83.65	$83.65	$83.70
Purchase #4	$128.57	13.328%	$145.7058	$145.71	$145.70	$145.70
Purchase #5	$141.88	4.560%	$148.3497	$148.35	$148.35	$148.30
Purchase #6	$242.41	8.459%	$262.9155	$262.92	$262.90	$262.90
Purchase #7	$110.31	4.634%	$115.4218	$115.42	$115.40	$115.40
7 purchase totals =	$995.38		$1,084.0343	$1,084.04	$1,084.00	$1,084.00