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	$245.27	11.343%	$273.091	$273.09	$273.10	$273.10
Purchase #2	$75.93	13.113%	$85.8867	$85.89	$85.90	$85.90
Purchase #3	$216.58	13.276%	$245.3332	$245.33	$245.35	$245.30
Purchase #4	$244.81	12.693%	$275.8837	$275.88	$275.90	$275.90
Purchase #5	$129.69	11.808%	$145.0038	$145.00	$145.00	$145.00
Purchase #6	$181.73	10.548%	$200.8989	$200.90	$200.90	$200.90
Purchase #7	$24.49	9.559%	$26.831	$26.83	$26.85	$26.80
7 purchase totals =	$1,118.50		$1,252.9283	$1,252.92	$1,253.00	$1,252.90