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	$59.61	7.754%	$64.2322	$64.23	$64.25	$64.20
Purchase #2	$70.53	11.851%	$78.8885	$78.89	$78.90	$78.90
Purchase #3	$53.74	12.115%	$60.2506	$60.25	$60.25	$60.30
Purchase #4	$191.41	6.612%	$204.066	$204.07	$204.05	$204.10
Purchase #5	$104.62	8.400%	$113.4081	$113.41	$113.40	$113.40
Purchase #6	$78.49	5.742%	$82.9969	$83.00	$83.00	$83.00
Purchase #7	$82.90	10.285%	$91.4263	$91.43	$91.45	$91.40
7 purchase totals =	$641.30		$695.2686	$695.28	$695.30	$695.30