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	$182.41	4.329%	$190.3065	$190.31	$190.30	$190.30
Purchase #2	$175.96	7.738%	$189.5758	$189.58	$189.60	$189.60
Purchase #3	$136.85	11.181%	$152.1512	$152.15	$152.15	$152.20
Purchase #4	$7.63	4.186%	$7.9494	$7.95	$7.95	$7.90
Purchase #5	$65.62	9.178%	$71.6426	$71.64	$71.65	$71.60
Purchase #6	$162.41	8.357%	$175.9826	$175.98	$176.00	$176.00
Purchase #7	$200.90	4.333%	$209.605	$209.61	$209.60	$209.60
7 purchase totals =	$931.78		$997.2131	$997.22	$997.25	$997.20