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	$218.52	11.412%	$243.4575	$243.46	$243.45	$243.50
Purchase #2	$6.52	5.184%	$6.858	$6.86	$6.85	$6.90
Purchase #3	$179.86	4.851%	$188.585	$188.59	$188.60	$188.60
Purchase #4	$32.30	7.492%	$34.7199	$34.72	$34.70	$34.70
Purchase #5	$193.73	5.547%	$204.4762	$204.48	$204.50	$204.50
Purchase #6	$29.83	3.517%	$30.8791	$30.88	$30.90	$30.90
Purchase #7	$38.70	9.141%	$42.2376	$42.24	$42.25	$42.20
7 purchase totals =	$699.46		$751.2133	$751.23	$751.25	$751.30