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	$108.42	9.594%	$118.8218	$118.82	$118.80	$118.80
Purchase #2	$193.74	11.467%	$215.9562	$215.96	$215.95	$216.00
Purchase #3	$139.53	13.309%	$158.1	$158.10	$158.10	$158.10
Purchase #4	$44.60	3.657%	$46.231	$46.23	$46.25	$46.20
Purchase #5	$166.54	9.477%	$182.323	$182.32	$182.30	$182.30
Purchase #6	$101.83	9.521%	$111.5252	$111.53	$111.55	$111.50
Purchase #7	$37.45	10.479%	$41.3744	$41.37	$41.35	$41.40
7 purchase totals =	$792.11		$874.3316	$874.33	$874.30	$874.30