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	$154.26	11.145%	$171.4523	$171.45	$171.45	$171.50
Purchase #2	$70.81	5.303%	$74.5651	$74.57	$74.55	$74.60
Purchase #3	$130.63	3.224%	$134.8415	$134.84	$134.85	$134.80
Purchase #4	$191.30	12.743%	$215.6774	$215.68	$215.70	$215.70
Purchase #5	$55.33	7.390%	$59.4189	$59.42	$59.40	$59.40
Purchase #6	$158.82	4.123%	$165.3681	$165.37	$165.35	$165.40
Purchase #7	$91.83	12.868%	$103.6467	$103.65	$103.65	$103.60
7 purchase totals =	$852.98		$924.9700	$924.98	$924.95	$925.00