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	$34.58	8.528%	$37.529	$37.53	$37.55	$37.50
Purchase #2	$118.54	8.456%	$128.5637	$128.56	$128.55	$128.60
Purchase #3	$245.54	4.582%	$256.7906	$256.79	$256.80	$256.80
Purchase #4	$167.66	7.139%	$179.6292	$179.63	$179.65	$179.60
Purchase #5	$121.89	13.145%	$137.9124	$137.91	$137.90	$137.90
Purchase #6	$160.66	4.856%	$168.4616	$168.46	$168.45	$168.50
Purchase #7	$140.46	13.593%	$159.5527	$159.55	$159.55	$159.60
7 purchase totals =	$989.33		$1,068.4392	$1,068.43	$1,068.45	$1,068.50