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	$11.54	11.369%	$12.852	$12.85	$12.85	$12.90
Purchase #2	$223.81	4.227%	$233.2704	$233.27	$233.25	$233.30
Purchase #3	$195.84	5.243%	$206.1079	$206.11	$206.10	$206.10
Purchase #4	$153.53	9.617%	$168.295	$168.30	$168.30	$168.30
Purchase #5	$165.64	5.791%	$175.2322	$175.23	$175.25	$175.20
Purchase #6	$32.35	3.465%	$33.4709	$33.47	$33.45	$33.50
Purchase #7	$114.76	3.377%	$118.6354	$118.64	$118.65	$118.60
7 purchase totals =	$897.47		$947.8638	$947.87	$947.85	$947.90