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	$179.67	5.747%	$189.9956	$190.00	$190.00	$190.00
Purchase #2	$131.75	3.145%	$135.8935	$135.89	$135.90	$135.90
Purchase #3	$108.42	8.635%	$117.7821	$117.78	$117.80	$117.80
Purchase #4	$245.29	12.417%	$275.7477	$275.75	$275.75	$275.70
Purchase #5	$190.26	5.465%	$200.6577	$200.66	$200.65	$200.70
Purchase #6	$46.60	9.276%	$50.9226	$50.92	$50.90	$50.90
Purchase #7	$38.57	8.603%	$41.8882	$41.89	$41.90	$41.90
7 purchase totals =	$940.56		$1,012.8874	$1,012.89	$1,012.90	$1,012.90