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	$130.91	8.119%	$141.5386	$141.54	$141.55	$141.50
Purchase #2	$223.77	5.409%	$235.8737	$235.87	$235.85	$235.90
Purchase #3	$227.80	4.430%	$237.8915	$237.89	$237.90	$237.90
Purchase #4	$5.81	5.683%	$6.1402	$6.14	$6.15	$6.10
Purchase #5	$111.57	12.423%	$125.4303	$125.43	$125.45	$125.40
Purchase #6	$175.98	11.839%	$196.8143	$196.81	$196.80	$196.80
Purchase #7	$129.60	11.369%	$144.3342	$144.33	$144.35	$144.30
7 purchase totals =	$1,005.44		$1,088.0228	$1,088.01	$1,088.05	$1,087.90