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	$86.62	3.142%	$89.3416	$89.34	$89.35	$89.30
Purchase #2	$128.42	3.598%	$133.0406	$133.04	$133.05	$133.00
Purchase #3	$97.98	7.665%	$105.4902	$105.49	$105.50	$105.50
Purchase #4	$235.92	4.603%	$246.7794	$246.78	$246.80	$246.80
Purchase #5	$49.62	7.111%	$53.1485	$53.15	$53.15	$53.10
Purchase #6	$182.86	13.817%	$208.1258	$208.13	$208.15	$208.10
Purchase #7	$246.71	7.118%	$264.2708	$264.27	$264.25	$264.30
7 purchase totals =	$1,028.13		$1,100.1969	$1,100.20	$1,100.25	$1,100.10