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	$197.47	7.803%	$212.8786	$212.88	$212.90	$212.90
Purchase #2	$171.67	9.786%	$188.4696	$188.47	$188.45	$188.50
Purchase #3	$109.30	12.412%	$122.8663	$122.87	$122.85	$122.90
Purchase #4	$63.67	10.121%	$70.114	$70.11	$70.10	$70.10
Purchase #5	$51.39	8.630%	$55.825	$55.83	$55.85	$55.80
Purchase #6	$96.89	13.449%	$109.9207	$109.92	$109.90	$109.90
Purchase #7	$120.62	13.700%	$137.1449	$137.14	$137.15	$137.10
7 purchase totals =	$811.01		$897.2191	$897.22	$897.20	$897.20