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	$140.96	7.167%	$151.0626	$151.06	$151.05	$151.10
Purchase #2	$29.48	7.603%	$31.7214	$31.72	$31.70	$31.70
Purchase #3	$101.77	11.267%	$113.2364	$113.24	$113.25	$113.20
Purchase #4	$172.59	9.380%	$188.7789	$188.78	$188.80	$188.80
Purchase #5	$135.41	8.173%	$146.4771	$146.48	$146.50	$146.50
Purchase #6	$238.50	12.114%	$267.3919	$267.39	$267.40	$267.40
Purchase #7	$249.78	7.410%	$268.2887	$268.29	$268.30	$268.30
7 purchase totals =	$1,068.49		$1,166.9570	$1,166.96	$1,167.00	$1,167.00