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	$146.76	4.246%	$152.9914	$152.99	$153.00	$153.00
Purchase #2	$110.95	3.114%	$114.405	$114.41	$114.40	$114.40
Purchase #3	$193.95	11.561%	$216.3726	$216.37	$216.35	$216.40
Purchase #4	$36.47	10.348%	$40.2439	$40.24	$40.25	$40.20
Purchase #5	$39.37	5.376%	$41.4865	$41.49	$41.50	$41.50
Purchase #6	$78.74	4.572%	$82.34	$82.34	$82.35	$82.30
Purchase #7	$246.54	13.681%	$280.2691	$280.27	$280.25	$280.30
7 purchase totals =	$852.78		$928.1085	$928.11	$928.10	$928.10