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	$249.41	5.813%	$263.9082	$263.91	$263.90	$263.90
Purchase #2	$40.89	11.699%	$45.6737	$45.67	$45.65	$45.70
Purchase #3	$82.56	4.723%	$86.4593	$86.46	$86.45	$86.50
Purchase #4	$59.54	8.416%	$64.5509	$64.55	$64.55	$64.60
Purchase #5	$115.80	3.382%	$119.7164	$119.72	$119.70	$119.70
Purchase #6	$230.61	10.673%	$255.223	$255.22	$255.20	$255.20
Purchase #7	$55.41	10.614%	$61.2912	$61.29	$61.30	$61.30
7 purchase totals =	$834.22		$896.8227	$896.82	$896.75	$896.90