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	$212.42	7.729%	$228.8379	$228.84	$228.85	$228.80
Purchase #2	$244.82	3.809%	$254.1452	$254.15	$254.15	$254.10
Purchase #3	$216.95	12.760%	$244.6328	$244.63	$244.65	$244.60
Purchase #4	$175.32	8.509%	$190.238	$190.24	$190.25	$190.20
Purchase #5	$93.51	6.582%	$99.6648	$99.66	$99.65	$99.70
Purchase #6	$70.44	11.406%	$78.4744	$78.47	$78.45	$78.50
Purchase #7	$51.42	9.859%	$56.4895	$56.49	$56.50	$56.50
7 purchase totals =	$1,064.88		$1,152.4826	$1,152.48	$1,152.50	$1,152.40