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	$120.61	6.622%	$128.5968	$128.60	$128.60	$128.60
Purchase #2	$202.64	13.430%	$229.8546	$229.85	$229.85	$229.90
Purchase #3	$58.58	4.167%	$61.021	$61.02	$61.00	$61.00
Purchase #4	$214.33	12.220%	$240.5211	$240.52	$240.50	$240.50
Purchase #5	$58.87	4.166%	$61.3225	$61.32	$61.30	$61.30
Purchase #6	$124.88	4.355%	$130.3185	$130.32	$130.30	$130.30
Purchase #7	$173.37	6.437%	$184.5298	$184.53	$184.55	$184.50
7 purchase totals =	$953.28		$1,036.1643	$1,036.16	$1,036.10	$1,036.10