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	$180.92	5.814%	$191.4387	$191.44	$191.45	$191.40
Purchase #2	$148.30	11.595%	$165.4954	$165.50	$165.50	$165.50
Purchase #3	$59.73	3.413%	$61.7686	$61.77	$61.75	$61.80
Purchase #4	$195.33	11.765%	$218.3106	$218.31	$218.30	$218.30
Purchase #5	$52.53	5.389%	$55.3608	$55.36	$55.35	$55.40
Purchase #6	$193.32	12.731%	$217.9316	$217.93	$217.95	$217.90
Purchase #7	$166.92	3.747%	$173.1745	$173.17	$173.15	$173.20
7 purchase totals =	$997.05		$1,083.4802	$1,083.48	$1,083.45	$1,083.50