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	$160.64	13.146%	$181.7577	$181.76	$181.75	$181.80
Purchase #2	$145.51	3.112%	$150.0383	$150.04	$150.05	$150.00
Purchase #3	$83.59	10.491%	$92.3594	$92.36	$92.35	$92.40
Purchase #4	$111.30	11.277%	$123.8513	$123.85	$123.85	$123.90
Purchase #5	$171.58	7.741%	$184.862	$184.86	$184.85	$184.90
Purchase #6	$162.40	13.201%	$183.8384	$183.84	$183.85	$183.80
Purchase #7	$28.95	13.513%	$32.862	$32.86	$32.85	$32.90
7 purchase totals =	$863.97		$949.5691	$949.57	$949.55	$949.70