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	$67.51	10.197%	$74.394	$74.39	$74.40	$74.40
Purchase #2	$238.85	6.758%	$254.9915	$254.99	$255.00	$255.00
Purchase #3	$187.40	4.787%	$196.3708	$196.37	$196.35	$196.40
Purchase #4	$217.59	11.802%	$243.27	$243.27	$243.25	$243.30
Purchase #5	$238.76	4.462%	$249.4135	$249.41	$249.40	$249.40
Purchase #6	$13.28	3.314%	$13.7201	$13.72	$13.70	$13.70
Purchase #7	$137.76	13.130%	$155.8479	$155.85	$155.85	$155.80
7 purchase totals =	$1,101.15		$1,188.0078	$1,188.00	$1,187.95	$1,188.00