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	$41.56	11.526%	$46.3502	$46.35	$46.35	$46.40
Purchase #2	$172.79	10.556%	$191.0297	$191.03	$191.05	$191.00
Purchase #3	$101.62	3.811%	$105.4927	$105.49	$105.50	$105.50
Purchase #4	$123.72	13.269%	$140.1364	$140.14	$140.15	$140.10
Purchase #5	$235.28	12.544%	$264.7935	$264.79	$264.80	$264.80
Purchase #6	$69.43	4.574%	$72.6057	$72.61	$72.60	$72.60
Purchase #7	$129.27	9.484%	$141.53	$141.53	$141.55	$141.50
7 purchase totals =	$873.67		$961.9382	$961.94	$962.00	$961.90