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	$198.70	12.508%	$223.5534	$223.55	$223.55	$223.60
Purchase #2	$160.42	13.766%	$182.5034	$182.50	$182.50	$182.50
Purchase #3	$78.45	8.717%	$85.2885	$85.29	$85.30	$85.30
Purchase #4	$141.89	12.867%	$160.147	$160.15	$160.15	$160.10
Purchase #5	$237.64	8.772%	$258.4858	$258.49	$258.50	$258.50
Purchase #6	$199.47	11.222%	$221.8545	$221.85	$221.85	$221.90
Purchase #7	$68.94	4.341%	$71.9327	$71.93	$71.95	$71.90
7 purchase totals =	$1,085.51		$1,203.7653	$1,203.76	$1,203.80	$1,203.80