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	$153.73	13.842%	$175.0093	$175.01	$175.00	$175.00
Purchase #2	$119.97	3.595%	$124.2829	$124.28	$124.30	$124.30
Purchase #3	$37.77	13.635%	$42.9199	$42.92	$42.90	$42.90
Purchase #4	$123.89	11.342%	$137.9416	$137.94	$137.95	$137.90
Purchase #5	$182.81	3.632%	$189.4497	$189.45	$189.45	$189.40
Purchase #6	$196.94	7.566%	$211.8405	$211.84	$211.85	$211.80
Purchase #7	$234.60	9.852%	$257.7128	$257.71	$257.70	$257.70
7 purchase totals =	$1,049.71		$1,139.1567	$1,139.15	$1,139.15	$1,139.00