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	$151.87	3.342%	$156.9455	$156.95	$156.95	$156.90
Purchase #2	$222.74	12.625%	$250.8609	$250.86	$250.85	$250.90
Purchase #3	$189.76	4.510%	$198.3182	$198.32	$198.30	$198.30
Purchase #4	$119.65	6.520%	$127.4512	$127.45	$127.45	$127.50
Purchase #5	$118.76	5.265%	$125.0127	$125.01	$125.00	$125.00
Purchase #6	$101.60	4.300%	$105.9688	$105.97	$105.95	$106.00
Purchase #7	$14.36	13.163%	$16.2502	$16.25	$16.25	$16.30
7 purchase totals =	$918.74		$980.8075	$980.81	$980.75	$980.90