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	$69.52	4.749%	$72.8215	$72.82	$72.80	$72.80
Purchase #2	$170.43	10.220%	$187.8479	$187.85	$187.85	$187.80
Purchase #3	$224.62	8.749%	$244.272	$244.27	$244.25	$244.30
Purchase #4	$249.34	6.555%	$265.6842	$265.68	$265.70	$265.70
Purchase #5	$23.93	11.808%	$26.7557	$26.76	$26.75	$26.80
Purchase #6	$182.69	7.366%	$196.1469	$196.15	$196.15	$196.10
Purchase #7	$147.53	12.105%	$165.3885	$165.39	$165.40	$165.40
7 purchase totals =	$1,068.06		$1,158.9167	$1,158.92	$1,158.90	$1,158.90