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	$33.54	5.168%	$35.2733	$35.27	$35.25	$35.30
Purchase #2	$244.76	6.709%	$261.1809	$261.18	$261.20	$261.20
Purchase #3	$145.89	9.772%	$160.1464	$160.15	$160.15	$160.10
Purchase #4	$16.46	6.115%	$17.4665	$17.47	$17.45	$17.50
Purchase #5	$230.26	11.739%	$257.2902	$257.29	$257.30	$257.30
Purchase #6	$171.69	4.338%	$179.1379	$179.14	$179.15	$179.10
Purchase #7	$169.47	9.656%	$185.834	$185.83	$185.85	$185.80
7 purchase totals =	$1,012.07		$1,096.3292	$1,096.33	$1,096.35	$1,096.30