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	$207.33	13.473%	$235.2636	$235.26	$235.25	$235.30
Purchase #2	$209.49	6.804%	$223.7437	$223.74	$223.75	$223.70
Purchase #3	$186.58	5.485%	$196.8139	$196.81	$196.80	$196.80
Purchase #4	$106.88	12.371%	$120.1021	$120.10	$120.10	$120.10
Purchase #5	$145.89	6.755%	$155.7449	$155.74	$155.75	$155.70
Purchase #6	$151.51	9.422%	$165.7853	$165.79	$165.80	$165.80
Purchase #7	$39.64	5.702%	$41.9003	$41.90	$41.90	$41.90
7 purchase totals =	$1,047.32		$1,139.3538	$1,139.34	$1,139.35	$1,139.30