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	$198.29	11.602%	$221.2956	$221.30	$221.30	$221.30
Purchase #2	$174.87	13.516%	$198.5054	$198.51	$198.50	$198.50
Purchase #3	$136.96	12.342%	$153.8636	$153.86	$153.85	$153.90
Purchase #4	$200.53	7.573%	$215.7161	$215.72	$215.70	$215.70
Purchase #5	$65.56	11.333%	$72.9899	$72.99	$73.00	$73.00
Purchase #6	$193.39	3.139%	$199.4605	$199.46	$199.45	$199.50
Purchase #7	$11.71	8.729%	$12.7322	$12.73	$12.75	$12.70
7 purchase totals =	$981.31		$1,074.5633	$1,074.57	$1,074.55	$1,074.60