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	$64.42	12.151%	$72.2477	$72.25	$72.25	$72.20
Purchase #2	$248.48	7.422%	$266.9222	$266.92	$266.90	$266.90
Purchase #3	$98.95	6.342%	$105.2254	$105.23	$105.25	$105.20
Purchase #4	$120.76	3.431%	$124.9033	$124.90	$124.90	$124.90
Purchase #5	$136.77	8.512%	$148.4119	$148.41	$148.40	$148.40
Purchase #6	$227.96	10.523%	$251.9482	$251.95	$251.95	$251.90
Purchase #7	$125.55	13.435%	$142.4176	$142.42	$142.40	$142.40
7 purchase totals =	$1,022.89		$1,112.0763	$1,112.08	$1,112.05	$1,111.90