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	$203.87	5.583%	$215.2521	$215.25	$215.25	$215.30
Purchase #2	$215.99	10.540%	$238.7553	$238.76	$238.75	$238.80
Purchase #3	$134.87	12.185%	$151.3039	$151.30	$151.30	$151.30
Purchase #4	$129.87	3.283%	$134.1336	$134.13	$134.15	$134.10
Purchase #5	$149.97	11.621%	$167.398	$167.40	$167.40	$167.40
Purchase #6	$10.82	9.319%	$11.8283	$11.83	$11.85	$11.80
Purchase #7	$167.77	8.460%	$181.9633	$181.96	$181.95	$182.00
7 purchase totals =	$1,013.16		$1,100.6345	$1,100.63	$1,100.65	$1,100.70