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	$225.65	7.400%	$242.3481	$242.35	$242.35	$242.30
Purchase #2	$160.36	5.725%	$169.5406	$169.54	$169.55	$169.50
Purchase #3	$34.71	8.379%	$37.6184	$37.62	$37.60	$37.60
Purchase #4	$217.55	11.654%	$242.9033	$242.90	$242.90	$242.90
Purchase #5	$178.34	10.418%	$196.9195	$196.92	$196.90	$196.90
Purchase #6	$140.66	8.809%	$153.0507	$153.05	$153.05	$153.10
Purchase #7	$110.78	5.417%	$116.781	$116.78	$116.80	$116.80
7 purchase totals =	$1,068.05		$1,159.1616	$1,159.16	$1,159.15	$1,159.10