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	$51.58	11.392%	$57.456	$57.46	$57.45	$57.50
Purchase #2	$9.73	11.658%	$10.8643	$10.86	$10.85	$10.90
Purchase #3	$220.50	11.358%	$245.5444	$245.54	$245.55	$245.50
Purchase #4	$114.79	10.253%	$126.5594	$126.56	$126.55	$126.60
Purchase #5	$142.81	6.680%	$152.3497	$152.35	$152.35	$152.30
Purchase #6	$71.68	12.774%	$80.8364	$80.84	$80.85	$80.80
Purchase #7	$218.91	10.420%	$241.7204	$241.72	$241.70	$241.70
7 purchase totals =	$830.00		$915.3306	$915.33	$915.30	$915.30