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	$67.79	7.259%	$72.7109	$72.71	$72.70	$72.70
Purchase #2	$31.98	6.629%	$34.1	$34.10	$34.10	$34.10
Purchase #3	$147.57	13.489%	$167.4757	$167.48	$167.50	$167.50
Purchase #4	$115.43	10.827%	$127.9276	$127.93	$127.95	$127.90
Purchase #5	$223.52	9.557%	$244.8818	$244.88	$244.90	$244.90
Purchase #6	$154.58	7.620%	$166.359	$166.36	$166.35	$166.40
Purchase #7	$61.55	11.735%	$68.7729	$68.77	$68.75	$68.80
7 purchase totals =	$802.42		$882.2279	$882.23	$882.25	$882.30