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	$147.69	6.191%	$156.8335	$156.83	$156.85	$156.80
Purchase #2	$171.69	9.766%	$188.4572	$188.46	$188.45	$188.50
Purchase #3	$57.91	8.511%	$62.8387	$62.84	$62.85	$62.80
Purchase #4	$168.50	10.259%	$185.7864	$185.79	$185.80	$185.80
Purchase #5	$225.46	9.871%	$247.7152	$247.72	$247.70	$247.70
Purchase #6	$33.67	12.589%	$37.9087	$37.91	$37.90	$37.90
Purchase #7	$60.31	6.441%	$64.1946	$64.19	$64.20	$64.20
7 purchase totals =	$865.23		$943.7343	$943.74	$943.75	$943.70