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	$169.47	12.743%	$191.0656	$191.07	$191.05	$191.10
Purchase #2	$111.33	7.580%	$119.7688	$119.77	$119.75	$119.80
Purchase #3	$185.52	6.445%	$197.4768	$197.48	$197.50	$197.50
Purchase #4	$96.67	4.634%	$101.1497	$101.15	$101.15	$101.10
Purchase #5	$236.35	11.334%	$263.1379	$263.14	$263.15	$263.10
Purchase #6	$213.59	9.513%	$233.9088	$233.91	$233.90	$233.90
Purchase #7	$33.79	11.591%	$37.7066	$37.71	$37.70	$37.70
7 purchase totals =	$1,046.72		$1,144.2142	$1,144.23	$1,144.20	$1,144.20