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	$35.85	4.363%	$37.4141	$37.41	$37.40	$37.40
Purchase #2	$57.58	8.241%	$62.3252	$62.33	$62.35	$62.30
Purchase #3	$92.71	8.230%	$100.34	$100.34	$100.35	$100.30
Purchase #4	$32.93	9.270%	$35.9826	$35.98	$36.00	$36.00
Purchase #5	$75.31	10.628%	$83.3139	$83.31	$83.30	$83.30
Purchase #6	$105.55	11.837%	$118.044	$118.04	$118.05	$118.00
Purchase #7	$144.53	10.140%	$159.1853	$159.19	$159.20	$159.20
7 purchase totals =	$544.46		$596.6051	$596.60	$596.65	$596.50