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	$222.51	7.162%	$238.4462	$238.45	$238.45	$238.40
Purchase #2	$222.54	9.452%	$243.5745	$243.57	$243.55	$243.60
Purchase #3	$160.25	11.546%	$178.7525	$178.75	$178.75	$178.80
Purchase #4	$235.64	8.441%	$255.5304	$255.53	$255.55	$255.50
Purchase #5	$177.36	4.599%	$185.5168	$185.52	$185.50	$185.50
Purchase #6	$213.62	4.595%	$223.4358	$223.44	$223.45	$223.40
Purchase #7	$91.43	9.510%	$100.125	$100.13	$100.15	$100.10
7 purchase totals =	$1,323.35		$1,425.3812	$1,425.39	$1,425.40	$1,425.30