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	$200.67	4.709%	$210.1196	$210.12	$210.10	$210.10
Purchase #2	$47.39	12.634%	$53.3773	$53.38	$53.40	$53.40
Purchase #3	$130.39	9.624%	$142.9387	$142.94	$142.95	$142.90
Purchase #4	$128.91	11.280%	$143.451	$143.45	$143.45	$143.50
Purchase #5	$131.42	10.123%	$144.7236	$144.72	$144.70	$144.70
Purchase #6	$96.49	8.537%	$104.7274	$104.73	$104.75	$104.70
Purchase #7	$157.92	6.520%	$168.2164	$168.22	$168.20	$168.20
7 purchase totals =	$893.19		$967.5540	$967.56	$967.55	$967.50