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	$114.76	10.821%	$127.1782	$127.18	$127.20	$127.20
Purchase #2	$74.36	4.826%	$77.9486	$77.95	$77.95	$77.90
Purchase #3	$233.45	10.768%	$258.5879	$258.59	$258.60	$258.60
Purchase #4	$113.82	10.388%	$125.6436	$125.64	$125.65	$125.60
Purchase #5	$234.88	4.842%	$246.2529	$246.25	$246.25	$246.30
Purchase #6	$71.48	11.308%	$79.563	$79.56	$79.55	$79.60
Purchase #7	$53.30	11.224%	$59.2824	$59.28	$59.30	$59.30
7 purchase totals =	$896.05		$974.4566	$974.45	$974.50	$974.50