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	$203.96	3.571%	$211.2434	$211.24	$211.25	$211.20
Purchase #2	$72.90	8.565%	$79.1439	$79.14	$79.15	$79.10
Purchase #3	$48.87	3.194%	$50.4309	$50.43	$50.45	$50.40
Purchase #4	$238.53	7.532%	$256.4961	$256.50	$256.50	$256.50
Purchase #5	$156.47	11.417%	$174.3342	$174.33	$174.35	$174.30
Purchase #6	$124.74	12.722%	$140.6094	$140.61	$140.60	$140.60
Purchase #7	$150.92	10.183%	$166.2882	$166.29	$166.30	$166.30
7 purchase totals =	$996.39		$1,078.5461	$1,078.54	$1,078.60	$1,078.40