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	$101.69	10.605%	$112.4742	$112.47	$112.45	$112.50
Purchase #2	$114.38	11.442%	$127.4674	$127.47	$127.45	$127.50
Purchase #3	$240.49	10.521%	$265.792	$265.79	$265.80	$265.80
Purchase #4	$57.37	7.609%	$61.7353	$61.74	$61.75	$61.70
Purchase #5	$249.67	13.357%	$283.0184	$283.02	$283.00	$283.00
Purchase #6	$243.49	13.775%	$277.0307	$277.03	$277.05	$277.00
Purchase #7	$39.50	6.755%	$42.1682	$42.17	$42.15	$42.20
7 purchase totals =	$1,046.59		$1,169.6862	$1,169.69	$1,169.65	$1,169.70