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	$31.67	13.254%	$35.8675	$35.87	$35.85	$35.90
Purchase #2	$91.75	12.519%	$103.2362	$103.24	$103.25	$103.20
Purchase #3	$149.49	13.833%	$170.169	$170.17	$170.15	$170.20
Purchase #4	$65.76	9.518%	$72.019	$72.02	$72.00	$72.00
Purchase #5	$250.77	3.320%	$259.0956	$259.10	$259.10	$259.10
Purchase #6	$136.39	11.360%	$151.8839	$151.88	$151.90	$151.90
Purchase #7	$146.37	6.237%	$155.4991	$155.50	$155.50	$155.50
7 purchase totals =	$872.20		$947.7703	$947.78	$947.75	$947.80