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	$203.35	7.864%	$219.3414	$219.34	$219.35	$219.30
Purchase #2	$93.88	7.181%	$100.6215	$100.62	$100.60	$100.60
Purchase #3	$241.49	9.801%	$265.1584	$265.16	$265.15	$265.20
Purchase #4	$100.39	9.854%	$110.2824	$110.28	$110.30	$110.30
Purchase #5	$185.74	4.739%	$194.5422	$194.54	$194.55	$194.50
Purchase #6	$12.63	5.324%	$13.3024	$13.30	$13.30	$13.30
Purchase #7	$100.42	12.412%	$112.8841	$112.88	$112.90	$112.90
7 purchase totals =	$937.90		$1,016.1324	$1,016.12	$1,016.15	$1,016.10