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	$127.48	4.188%	$132.8189	$132.82	$132.80	$132.80
Purchase #2	$229.47	9.225%	$250.6386	$250.64	$250.65	$250.60
Purchase #3	$162.74	3.783%	$168.8965	$168.90	$168.90	$168.90
Purchase #4	$169.49	12.775%	$191.1423	$191.14	$191.15	$191.10
Purchase #5	$225.78	10.130%	$248.6515	$248.65	$248.65	$248.70
Purchase #6	$142.39	10.627%	$157.5218	$157.52	$157.50	$157.50
Purchase #7	$93.31	11.848%	$104.3654	$104.37	$104.35	$104.40
7 purchase totals =	$1,150.66		$1,254.0350	$1,254.04	$1,254.00	$1,254.00