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	$147.77	5.482%	$155.8708	$155.87	$155.85	$155.90
Purchase #2	$29.89	8.521%	$32.4369	$32.44	$32.45	$32.40
Purchase #3	$72.97	12.246%	$81.9059	$81.91	$81.90	$81.90
Purchase #4	$174.40	12.446%	$196.1058	$196.11	$196.10	$196.10
Purchase #5	$160.40	12.284%	$180.1035	$180.10	$180.10	$180.10
Purchase #6	$28.63	5.160%	$30.1073	$30.11	$30.10	$30.10
Purchase #7	$50.25	5.137%	$52.8313	$52.83	$52.85	$52.80
7 purchase totals =	$664.31		$729.3615	$729.37	$729.35	$729.30