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	$111.82	4.675%	$117.0476	$117.05	$117.05	$117.00
Purchase #2	$78.26	10.485%	$86.4656	$86.47	$86.45	$86.50
Purchase #3	$139.66	3.705%	$144.8344	$144.83	$144.85	$144.80
Purchase #4	$89.77	6.441%	$95.5521	$95.55	$95.55	$95.60
Purchase #5	$94.35	6.525%	$100.5063	$100.51	$100.50	$100.50
Purchase #6	$164.41	6.766%	$175.534	$175.53	$175.55	$175.50
Purchase #7	$184.36	4.356%	$192.3907	$192.39	$192.40	$192.40
7 purchase totals =	$862.63		$912.3307	$912.33	$912.35	$912.30