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	$203.79	9.828%	$223.8185	$223.82	$223.80	$223.80
Purchase #2	$232.80	9.270%	$254.3806	$254.38	$254.40	$254.40
Purchase #3	$43.48	5.463%	$45.8553	$45.86	$45.85	$45.90
Purchase #4	$30.86	4.815%	$32.3459	$32.35	$32.35	$32.30
Purchase #5	$192.30	7.472%	$206.6687	$206.67	$206.65	$206.70
Purchase #6	$134.33	12.446%	$151.0487	$151.05	$151.05	$151.00
Purchase #7	$159.67	3.477%	$165.2217	$165.22	$165.20	$165.20
7 purchase totals =	$997.23		$1,079.3394	$1,079.35	$1,079.30	$1,079.30