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	$57.25	7.765%	$61.6955	$61.70	$61.70	$61.70
Purchase #2	$238.39	12.525%	$268.2483	$268.25	$268.25	$268.20
Purchase #3	$155.91	10.850%	$172.8262	$172.83	$172.85	$172.80
Purchase #4	$191.42	12.703%	$215.7361	$215.74	$215.75	$215.70
Purchase #5	$239.81	9.324%	$262.1699	$262.17	$262.15	$262.20
Purchase #6	$129.69	12.242%	$145.5666	$145.57	$145.55	$145.60
Purchase #7	$23.39	7.499%	$25.144	$25.14	$25.15	$25.10
7 purchase totals =	$1,035.86		$1,151.3866	$1,151.40	$1,151.40	$1,151.30