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	$33.55	10.440%	$37.0526	$37.05	$37.05	$37.10
Purchase #2	$37.62	11.526%	$41.9561	$41.96	$41.95	$42.00
Purchase #3	$166.85	10.347%	$184.114	$184.11	$184.10	$184.10
Purchase #4	$127.45	3.729%	$132.2026	$132.20	$132.20	$132.20
Purchase #5	$53.82	10.464%	$59.4517	$59.45	$59.45	$59.50
Purchase #6	$234.44	10.680%	$259.4782	$259.48	$259.50	$259.50
Purchase #7	$202.69	8.487%	$219.8923	$219.89	$219.90	$219.90
7 purchase totals =	$856.42		$934.1475	$934.14	$934.15	$934.30