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	$89.52	8.283%	$96.9349	$96.93	$96.95	$96.90
Purchase #2	$237.50	3.338%	$245.4278	$245.43	$245.45	$245.40
Purchase #3	$99.31	12.298%	$111.5231	$111.52	$111.50	$111.50
Purchase #4	$143.42	12.306%	$161.0693	$161.07	$161.05	$161.10
Purchase #5	$221.61	8.346%	$240.1056	$240.11	$240.10	$240.10
Purchase #6	$221.69	8.561%	$240.6689	$240.67	$240.65	$240.70
Purchase #7	$19.38	5.765%	$20.4973	$20.50	$20.50	$20.50
7 purchase totals =	$1,032.43		$1,116.2269	$1,116.23	$1,116.20	$1,116.20