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	$117.67	10.555%	$130.0901	$130.09	$130.10	$130.10
Purchase #2	$74.30	3.278%	$76.7356	$76.74	$76.75	$76.70
Purchase #3	$95.27	11.160%	$105.9021	$105.90	$105.90	$105.90
Purchase #4	$40.69	5.335%	$42.8608	$42.86	$42.85	$42.90
Purchase #5	$30.63	7.420%	$32.9027	$32.90	$32.90	$32.90
Purchase #6	$49.49	4.610%	$51.7715	$51.77	$51.75	$51.80
Purchase #7	$135.91	10.775%	$150.5543	$150.55	$150.55	$150.60
7 purchase totals =	$543.96		$590.8171	$590.81	$590.80	$590.90