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	$215.37	4.623%	$225.3266	$225.33	$225.35	$225.30
Purchase #2	$65.86	9.842%	$72.3419	$72.34	$72.35	$72.30
Purchase #3	$226.31	13.485%	$256.8279	$256.83	$256.85	$256.80
Purchase #4	$75.54	10.575%	$83.5284	$83.53	$83.55	$83.50
Purchase #5	$178.70	5.299%	$188.1693	$188.17	$188.15	$188.20
Purchase #6	$131.50	12.107%	$147.4207	$147.42	$147.40	$147.40
Purchase #7	$220.53	12.280%	$247.6111	$247.61	$247.60	$247.60
7 purchase totals =	$1,113.81		$1,221.2259	$1,221.23	$1,221.25	$1,221.10