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	$222.32	6.864%	$237.58	$237.58	$237.60	$237.60
Purchase #2	$62.27	4.530%	$65.0908	$65.09	$65.10	$65.10
Purchase #3	$133.91	5.392%	$141.1304	$141.13	$141.15	$141.10
Purchase #4	$70.82	10.190%	$78.0366	$78.04	$78.05	$78.00
Purchase #5	$138.38	10.417%	$152.795	$152.80	$152.80	$152.80
Purchase #6	$169.51	7.803%	$182.7369	$182.74	$182.75	$182.70
Purchase #7	$201.50	7.408%	$216.4271	$216.43	$216.45	$216.40
7 purchase totals =	$998.71		$1,073.7968	$1,073.81	$1,073.90	$1,073.70