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	$196.96	13.643%	$223.8313	$223.83	$223.85	$223.80
Purchase #2	$147.44	3.518%	$152.6269	$152.63	$152.65	$152.60
Purchase #3	$58.39	7.651%	$62.8574	$62.86	$62.85	$62.90
Purchase #4	$83.46	7.382%	$89.621	$89.62	$89.60	$89.60
Purchase #5	$15.70	12.519%	$17.6655	$17.67	$17.65	$17.70
Purchase #6	$211.73	7.625%	$227.8744	$227.87	$227.85	$227.90
Purchase #7	$159.96	13.300%	$181.2347	$181.23	$181.25	$181.20
7 purchase totals =	$873.64		$955.7112	$955.71	$955.70	$955.70