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	$209.61	11.194%	$233.0737	$233.07	$233.05	$233.10
Purchase #2	$159.31	6.793%	$170.1319	$170.13	$170.15	$170.10
Purchase #3	$55.63	11.811%	$62.2005	$62.20	$62.20	$62.20
Purchase #4	$44.64	7.300%	$47.8987	$47.90	$47.90	$47.90
Purchase #5	$137.28	8.456%	$148.8884	$148.89	$148.90	$148.90
Purchase #6	$64.58	12.728%	$72.7997	$72.80	$72.80	$72.80
Purchase #7	$82.55	3.868%	$85.743	$85.74	$85.75	$85.70
7 purchase totals =	$753.60		$820.7359	$820.73	$820.75	$820.70