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	$119.25	10.119%	$131.3169	$131.32	$131.30	$131.30
Purchase #2	$170.31	11.771%	$190.3572	$190.36	$190.35	$190.40
Purchase #3	$241.67	9.389%	$264.3604	$264.36	$264.35	$264.40
Purchase #4	$210.58	10.301%	$232.2718	$232.27	$232.25	$232.30
Purchase #5	$65.38	10.513%	$72.2534	$72.25	$72.25	$72.30
Purchase #6	$160.59	6.157%	$170.4775	$170.48	$170.50	$170.50
Purchase #7	$183.42	3.230%	$189.3445	$189.34	$189.35	$189.30
7 purchase totals =	$1,151.20		$1,250.3817	$1,250.38	$1,250.35	$1,250.50