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	$79.47	7.315%	$85.2832	$85.28	$85.30	$85.30
Purchase #2	$80.82	13.130%	$91.4317	$91.43	$91.45	$91.40
Purchase #3	$70.61	11.118%	$78.4604	$78.46	$78.45	$78.50
Purchase #4	$8.33	8.570%	$9.0439	$9.04	$9.05	$9.00
Purchase #5	$25.42	11.301%	$28.2927	$28.29	$28.30	$28.30
Purchase #6	$94.97	7.766%	$102.3454	$102.35	$102.35	$102.30
Purchase #7	$65.66	12.380%	$73.7887	$73.79	$73.80	$73.80
7 purchase totals =	$425.28		$468.6460	$468.64	$468.70	$468.60