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	$171.67	8.216%	$185.7744	$185.77	$185.75	$185.80
Purchase #2	$62.95	7.776%	$67.845	$67.85	$67.85	$67.80
Purchase #3	$28.69	4.550%	$29.9954	$30.00	$30.00	$30.00
Purchase #4	$187.25	6.145%	$198.7565	$198.76	$198.75	$198.80
Purchase #5	$192.75	7.126%	$206.4854	$206.49	$206.50	$206.50
Purchase #6	$113.59	3.411%	$117.4646	$117.46	$117.45	$117.50
Purchase #7	$234.50	8.717%	$254.9414	$254.94	$254.95	$254.90
7 purchase totals =	$991.40		$1,061.2627	$1,061.27	$1,061.25	$1,061.30