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	$73.74	6.635%	$78.6326	$78.63	$78.65	$78.60
Purchase #2	$54.46	5.696%	$57.562	$57.56	$57.55	$57.60
Purchase #3	$40.53	7.112%	$43.4125	$43.41	$43.40	$43.40
Purchase #4	$124.85	6.188%	$132.5757	$132.58	$132.60	$132.60
Purchase #5	$60.55	7.307%	$64.9744	$64.97	$64.95	$65.00
Purchase #6	$140.33	10.785%	$155.4646	$155.46	$155.45	$155.50
Purchase #7	$26.60	3.711%	$27.5871	$27.59	$27.60	$27.60
7 purchase totals =	$521.06		$560.2089	$560.20	$560.20	$560.30