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	$95.87	4.842%	$100.512	$100.51	$100.50	$100.50
Purchase #2	$37.94	4.523%	$39.656	$39.66	$39.65	$39.70
Purchase #3	$185.67	5.336%	$195.5774	$195.58	$195.60	$195.60
Purchase #4	$104.27	6.406%	$110.9495	$110.95	$110.95	$110.90
Purchase #5	$151.52	6.615%	$161.543	$161.54	$161.55	$161.50
Purchase #6	$156.75	6.113%	$166.3321	$166.33	$166.35	$166.30
Purchase #7	$235.49	3.381%	$243.4519	$243.45	$243.45	$243.50
7 purchase totals =	$967.51		$1,018.0219	$1,018.02	$1,018.05	$1,018.00