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	$237.60	9.637%	$260.4975	$260.50	$260.50	$260.50
Purchase #2	$111.35	5.281%	$117.2304	$117.23	$117.25	$117.20
Purchase #3	$94.74	13.394%	$107.4295	$107.43	$107.45	$107.40
Purchase #4	$145.83	3.478%	$150.902	$150.90	$150.90	$150.90
Purchase #5	$125.45	4.830%	$131.5092	$131.51	$131.50	$131.50
Purchase #6	$94.85	5.770%	$100.3228	$100.32	$100.30	$100.30
Purchase #7	$169.77	9.136%	$185.2802	$185.28	$185.30	$185.30
7 purchase totals =	$979.59		$1,053.1716	$1,053.17	$1,053.20	$1,053.10