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	$238.97	10.865%	$264.9341	$264.93	$264.95	$264.90
Purchase #2	$229.43	6.730%	$244.8706	$244.87	$244.85	$244.90
Purchase #3	$78.93	13.141%	$89.3022	$89.30	$89.30	$89.30
Purchase #4	$161.38	13.216%	$182.708	$182.71	$182.70	$182.70
Purchase #5	$57.64	11.775%	$64.4271	$64.43	$64.45	$64.40
Purchase #6	$58.43	5.620%	$61.7138	$61.71	$61.70	$61.70
Purchase #7	$181.25	8.485%	$196.6291	$196.63	$196.65	$196.60
7 purchase totals =	$1,006.03		$1,104.5849	$1,104.58	$1,104.60	$1,104.50