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	$79.26	7.640%	$85.3155	$85.32	$85.30	$85.30
Purchase #2	$75.70	8.441%	$82.0898	$82.09	$82.10	$82.10
Purchase #3	$40.57	5.537%	$42.8164	$42.82	$42.80	$42.80
Purchase #4	$127.86	5.476%	$134.8616	$134.86	$134.85	$134.90
Purchase #5	$236.28	11.801%	$264.1634	$264.16	$264.15	$264.20
Purchase #6	$130.56	11.139%	$145.1031	$145.10	$145.10	$145.10
Purchase #7	$202.25	9.633%	$221.7327	$221.73	$221.75	$221.70
7 purchase totals =	$892.48		$976.0825	$976.08	$976.05	$976.10