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	$113.44	12.253%	$127.3398	$127.34	$127.35	$127.30
Purchase #2	$94.43	7.378%	$101.397	$101.40	$101.40	$101.40
Purchase #3	$41.72	5.224%	$43.8995	$43.90	$43.90	$43.90
Purchase #4	$228.71	10.434%	$252.5736	$252.57	$252.55	$252.60
Purchase #5	$59.56	3.517%	$61.6547	$61.65	$61.65	$61.70
Purchase #6	$14.97	4.520%	$15.6466	$15.65	$15.65	$15.60
Purchase #7	$57.35	4.197%	$59.757	$59.76	$59.75	$59.80
7 purchase totals =	$610.18		$662.2682	$662.27	$662.25	$662.30