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	$147.34	7.839%	$158.89	$158.89	$158.90	$158.90
Purchase #2	$243.28	7.447%	$261.3971	$261.40	$261.40	$261.40
Purchase #3	$127.76	5.872%	$135.2621	$135.26	$135.25	$135.30
Purchase #4	$214.62	3.704%	$222.5695	$222.57	$222.55	$222.60
Purchase #5	$209.48	6.192%	$222.451	$222.45	$222.45	$222.50
Purchase #6	$152.35	5.522%	$160.7628	$160.76	$160.75	$160.80
Purchase #7	$54.63	13.413%	$61.9575	$61.96	$61.95	$62.00
7 purchase totals =	$1,149.46		$1,223.2900	$1,223.29	$1,223.25	$1,223.50