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	$63.97	5.774%	$67.6636	$67.66	$67.65	$67.70
Purchase #2	$51.97	3.496%	$53.7869	$53.79	$53.80	$53.80
Purchase #3	$65.77	9.279%	$71.8728	$71.87	$71.85	$71.90
Purchase #4	$126.96	11.470%	$141.5223	$141.52	$141.50	$141.50
Purchase #5	$197.76	12.716%	$222.9072	$222.91	$222.90	$222.90
Purchase #6	$44.72	5.419%	$47.1434	$47.14	$47.15	$47.10
Purchase #7	$126.60	10.342%	$139.693	$139.69	$139.70	$139.70
7 purchase totals =	$677.75		$744.5892	$744.58	$744.55	$744.60