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	$38.62	7.174%	$41.3906	$41.39	$41.40	$41.40
Purchase #2	$37.52	13.162%	$42.4584	$42.46	$42.45	$42.50
Purchase #3	$144.48	12.456%	$162.4764	$162.48	$162.50	$162.50
Purchase #4	$165.47	4.470%	$172.8665	$172.87	$172.85	$172.90
Purchase #5	$184.35	5.114%	$193.7777	$193.78	$193.80	$193.80
Purchase #6	$172.89	6.359%	$183.8841	$183.88	$183.90	$183.90
Purchase #7	$202.87	5.217%	$213.4537	$213.45	$213.45	$213.50
7 purchase totals =	$946.20		$1,010.3074	$1,010.31	$1,010.35	$1,010.50