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	$169.87	12.401%	$190.9356	$190.94	$190.95	$190.90
Purchase #2	$167.65	7.518%	$180.2539	$180.25	$180.25	$180.30
Purchase #3	$170.96	10.384%	$188.7125	$188.71	$188.70	$188.70
Purchase #4	$173.75	6.144%	$184.4252	$184.43	$184.45	$184.40
Purchase #5	$38.95	10.211%	$42.9272	$42.93	$42.95	$42.90
Purchase #6	$213.50	3.773%	$221.5554	$221.56	$221.55	$221.60
Purchase #7	$71.61	7.736%	$77.1497	$77.15	$77.15	$77.10
7 purchase totals =	$1,006.29		$1,085.9595	$1,085.97	$1,086.00	$1,085.90