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	$191.33	11.178%	$212.7169	$212.72	$212.70	$212.70
Purchase #2	$46.62	9.181%	$50.9002	$50.90	$50.90	$50.90
Purchase #3	$49.92	13.791%	$56.8045	$56.80	$56.80	$56.80
Purchase #4	$133.90	5.492%	$141.2538	$141.25	$141.25	$141.30
Purchase #5	$156.73	9.563%	$171.7181	$171.72	$171.70	$171.70
Purchase #6	$145.40	5.589%	$153.5264	$153.53	$153.55	$153.50
Purchase #7	$210.95	3.175%	$217.6477	$217.65	$217.65	$217.60
7 purchase totals =	$934.85		$1,004.5676	$1,004.57	$1,004.55	$1,004.50