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	$50.56	10.278%	$55.7566	$55.76	$55.75	$55.80
Purchase #2	$99.87	5.649%	$105.5117	$105.51	$105.50	$105.50
Purchase #3	$166.54	3.442%	$172.2723	$172.27	$172.25	$172.30
Purchase #4	$41.59	8.372%	$45.0719	$45.07	$45.05	$45.10
Purchase #5	$145.44	13.111%	$164.5086	$164.51	$164.50	$164.50
Purchase #6	$47.50	4.314%	$49.5492	$49.55	$49.55	$49.50
Purchase #7	$57.95	7.182%	$62.112	$62.11	$62.10	$62.10
7 purchase totals =	$609.45		$654.7823	$654.78	$654.70	$654.80