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	$162.54	12.768%	$183.2931	$183.29	$183.30	$183.30
Purchase #2	$185.84	6.589%	$198.085	$198.09	$198.10	$198.10
Purchase #3	$130.92	6.306%	$139.1758	$139.18	$139.20	$139.20
Purchase #4	$177.39	13.487%	$201.3146	$201.31	$201.30	$201.30
Purchase #5	$203.56	9.289%	$222.4687	$222.47	$222.45	$222.50
Purchase #6	$85.55	11.633%	$95.502	$95.50	$95.50	$95.50
Purchase #7	$94.89	10.165%	$104.5356	$104.54	$104.55	$104.50
7 purchase totals =	$1,040.69		$1,144.3748	$1,144.38	$1,144.40	$1,144.40