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	$184.52	6.611%	$196.7186	$196.72	$196.70	$196.70
Purchase #2	$127.59	13.535%	$144.8593	$144.86	$144.85	$144.90
Purchase #3	$6.65	5.541%	$7.0185	$7.02	$7.00	$7.00
Purchase #4	$99.30	4.578%	$103.846	$103.85	$103.85	$103.80
Purchase #5	$51.65	7.525%	$55.5367	$55.54	$55.55	$55.50
Purchase #6	$65.51	12.650%	$73.797	$73.80	$73.80	$73.80
Purchase #7	$204.30	8.834%	$222.3479	$222.35	$222.35	$222.30
7 purchase totals =	$739.52		$804.1240	$804.14	$804.10	$804.00