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	$139.45	6.735%	$148.842	$148.84	$148.85	$148.80
Purchase #2	$80.50	9.477%	$88.129	$88.13	$88.15	$88.10
Purchase #3	$35.25	7.157%	$37.7728	$37.77	$37.75	$37.80
Purchase #4	$60.92	6.730%	$65.0199	$65.02	$65.00	$65.00
Purchase #5	$35.25	11.516%	$39.3094	$39.31	$39.30	$39.30
Purchase #6	$101.45	6.825%	$108.374	$108.37	$108.35	$108.40
Purchase #7	$28.48	11.561%	$31.7726	$31.77	$31.75	$31.80
7 purchase totals =	$481.30		$519.2197	$519.21	$519.15	$519.20