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	$211.72	4.539%	$221.33	$221.33	$221.35	$221.30
Purchase #2	$192.66	9.242%	$210.4656	$210.47	$210.45	$210.50
Purchase #3	$186.87	12.117%	$209.513	$209.51	$209.50	$209.50
Purchase #4	$103.43	7.718%	$111.4127	$111.41	$111.40	$111.40
Purchase #5	$218.72	9.663%	$239.8549	$239.85	$239.85	$239.90
Purchase #6	$81.73	4.318%	$85.2591	$85.26	$85.25	$85.30
Purchase #7	$232.72	11.330%	$259.0872	$259.09	$259.10	$259.10
7 purchase totals =	$1,227.85		$1,336.9225	$1,336.92	$1,336.90	$1,337.00