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	$64.47	13.113%	$72.924	$72.92	$72.90	$72.90
Purchase #2	$165.73	3.165%	$170.9754	$170.98	$171.00	$171.00
Purchase #3	$33.58	4.262%	$35.0112	$35.01	$35.00	$35.00
Purchase #4	$95.61	10.437%	$105.5888	$105.59	$105.60	$105.60
Purchase #5	$177.67	4.456%	$185.587	$185.59	$185.60	$185.60
Purchase #6	$220.29	9.716%	$241.6934	$241.69	$241.70	$241.70
Purchase #7	$231.63	10.572%	$256.1179	$256.12	$256.10	$256.10
7 purchase totals =	$988.98		$1,067.8977	$1,067.90	$1,067.90	$1,067.90