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	$198.48	13.371%	$225.0188	$225.02	$225.00	$225.00
Purchase #2	$236.51	8.264%	$256.0552	$256.06	$256.05	$256.10
Purchase #3	$166.29	9.709%	$182.4351	$182.44	$182.45	$182.40
Purchase #4	$121.33	5.190%	$127.627	$127.63	$127.65	$127.60
Purchase #5	$93.72	7.301%	$100.5625	$100.56	$100.55	$100.60
Purchase #6	$170.67	4.848%	$178.9441	$178.94	$178.95	$178.90
Purchase #7	$228.56	10.812%	$253.2719	$253.27	$253.25	$253.30
7 purchase totals =	$1,215.56		$1,323.9146	$1,323.92	$1,323.90	$1,323.90