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	$81.28	5.473%	$85.7285	$85.73	$85.75	$85.70
Purchase #2	$85.39	6.106%	$90.6039	$90.60	$90.60	$90.60
Purchase #3	$26.34	3.685%	$27.3106	$27.31	$27.30	$27.30
Purchase #4	$17.57	4.468%	$18.355	$18.36	$18.35	$18.40
Purchase #5	$145.69	4.131%	$151.7085	$151.71	$151.70	$151.70
Purchase #6	$81.32	11.450%	$90.6311	$90.63	$90.65	$90.60
Purchase #7	$147.97	12.522%	$166.4988	$166.50	$166.50	$166.50
7 purchase totals =	$585.56		$630.8364	$630.84	$630.85	$630.80