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	$36.39	3.366%	$37.6149	$37.61	$37.60	$37.60
Purchase #2	$247.72	11.750%	$276.8271	$276.83	$276.85	$276.80
Purchase #3	$164.80	6.184%	$174.9912	$174.99	$175.00	$175.00
Purchase #4	$95.48	10.283%	$105.2982	$105.30	$105.30	$105.30
Purchase #5	$235.62	12.178%	$264.3138	$264.31	$264.30	$264.30
Purchase #6	$70.78	10.158%	$77.9698	$77.97	$77.95	$78.00
Purchase #7	$167.72	7.171%	$179.7472	$179.75	$179.75	$179.70
7 purchase totals =	$1,018.51		$1,116.7622	$1,116.76	$1,116.75	$1,116.70