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	$33.74	4.151%	$35.1405	$35.14	$35.15	$35.10
Purchase #2	$215.56	9.548%	$236.1417	$236.14	$236.15	$236.10
Purchase #3	$45.89	9.198%	$50.111	$50.11	$50.10	$50.10
Purchase #4	$172.25	13.873%	$196.1462	$196.15	$196.15	$196.10
Purchase #5	$180.56	10.561%	$199.6289	$199.63	$199.65	$199.60
Purchase #6	$104.92	4.115%	$109.2375	$109.24	$109.25	$109.20
Purchase #7	$174.70	8.518%	$189.5809	$189.58	$189.60	$189.60
7 purchase totals =	$927.62		$1,015.9867	$1,015.99	$1,016.05	$1,015.80