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	$12.53	11.325%	$13.949	$13.95	$13.95	$13.90
Purchase #2	$55.44	11.216%	$61.6582	$61.66	$61.65	$61.70
Purchase #3	$148.83	5.245%	$156.6361	$156.64	$156.65	$156.60
Purchase #4	$206.41	10.373%	$227.8209	$227.82	$227.80	$227.80
Purchase #5	$135.91	12.788%	$153.2902	$153.29	$153.30	$153.30
Purchase #6	$37.56	11.444%	$41.8584	$41.86	$41.85	$41.90
Purchase #7	$144.43	7.483%	$155.2377	$155.24	$155.25	$155.20
7 purchase totals =	$741.11		$810.4505	$810.46	$810.45	$810.40