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	$17.46	10.522%	$19.2971	$19.30	$19.30	$19.30
Purchase #2	$68.56	4.776%	$71.8344	$71.83	$71.85	$71.80
Purchase #3	$93.37	12.111%	$104.678	$104.68	$104.70	$104.70
Purchase #4	$108.73	6.551%	$115.8529	$115.85	$115.85	$115.90
Purchase #5	$178.89	5.802%	$189.2692	$189.27	$189.25	$189.30
Purchase #6	$104.66	5.520%	$110.4372	$110.44	$110.45	$110.40
Purchase #7	$189.53	3.500%	$196.1636	$196.16	$196.15	$196.20
7 purchase totals =	$761.20		$807.5324	$807.53	$807.55	$807.60