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	$59.46	10.807%	$65.8858	$65.89	$65.90	$65.90
Purchase #2	$158.94	7.373%	$170.6586	$170.66	$170.65	$170.70
Purchase #3	$221.91	13.146%	$251.0823	$251.08	$251.10	$251.10
Purchase #4	$75.36	3.457%	$77.9652	$77.97	$77.95	$78.00
Purchase #5	$150.76	13.825%	$171.6026	$171.60	$171.60	$171.60
Purchase #6	$192.35	4.444%	$200.898	$200.90	$200.90	$200.90
Purchase #7	$196.68	10.764%	$217.8506	$217.85	$217.85	$217.90
7 purchase totals =	$1,055.46		$1,155.9431	$1,155.95	$1,155.95	$1,156.10