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	$194.45	7.216%	$208.4815	$208.48	$208.50	$208.50
Purchase #2	$136.65	4.320%	$142.5533	$142.55	$142.55	$142.60
Purchase #3	$30.95	4.180%	$32.2437	$32.24	$32.25	$32.20
Purchase #4	$136.99	10.578%	$151.4808	$151.48	$151.50	$151.50
Purchase #5	$33.70	12.267%	$37.834	$37.83	$37.85	$37.80
Purchase #6	$221.42	12.173%	$248.3735	$248.37	$248.35	$248.40
Purchase #7	$192.44	4.399%	$200.9054	$200.91	$200.90	$200.90
7 purchase totals =	$946.60		$1,021.8722	$1,021.86	$1,021.90	$1,021.90