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	$175.46	12.605%	$197.5767	$197.58	$197.60	$197.60
Purchase #2	$197.56	9.249%	$215.8323	$215.83	$215.85	$215.80
Purchase #3	$62.74	13.709%	$71.341	$71.34	$71.35	$71.30
Purchase #4	$228.54	12.246%	$256.527	$256.53	$256.55	$256.50
Purchase #5	$79.69	8.320%	$86.3202	$86.32	$86.30	$86.30
Purchase #6	$108.87	3.140%	$112.2885	$112.29	$112.30	$112.30
Purchase #7	$89.58	10.406%	$98.9017	$98.90	$98.90	$98.90
7 purchase totals =	$942.44		$1,038.7874	$1,038.79	$1,038.85	$1,038.70