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	$217.51	7.344%	$233.4839	$233.48	$233.50	$233.50
Purchase #2	$117.76	11.380%	$131.1611	$131.16	$131.15	$131.20
Purchase #3	$150.40	7.404%	$161.5356	$161.54	$161.55	$161.50
Purchase #4	$117.92	3.269%	$121.7748	$121.77	$121.75	$121.80
Purchase #5	$187.59	4.670%	$196.3505	$196.35	$196.35	$196.40
Purchase #6	$49.32	13.738%	$56.0956	$56.10	$56.10	$56.10
Purchase #7	$123.39	9.784%	$135.4625	$135.46	$135.45	$135.50
7 purchase totals =	$963.89		$1,035.8640	$1,035.86	$1,035.85	$1,036.00