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	$31.83	4.116%	$33.1401	$33.14	$33.15	$33.10
Purchase #2	$138.56	7.412%	$148.8301	$148.83	$148.85	$148.80
Purchase #3	$23.77	11.179%	$26.4272	$26.43	$26.45	$26.40
Purchase #4	$177.63	11.721%	$198.45	$198.45	$198.45	$198.50
Purchase #5	$33.28	11.369%	$37.0636	$37.06	$37.05	$37.10
Purchase #6	$164.52	5.601%	$173.7348	$173.73	$173.75	$173.70
Purchase #7	$118.70	3.781%	$123.188	$123.19	$123.20	$123.20
7 purchase totals =	$688.29		$740.8338	$740.83	$740.90	$740.80