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	$127.60	13.584%	$144.9332	$144.93	$144.95	$144.90
Purchase #2	$238.54	7.480%	$256.3828	$256.38	$256.40	$256.40
Purchase #3	$236.66	9.369%	$258.8327	$258.83	$258.85	$258.80
Purchase #4	$250.25	6.517%	$266.5588	$266.56	$266.55	$266.60
Purchase #5	$98.72	6.807%	$105.4399	$105.44	$105.45	$105.40
Purchase #6	$45.51	11.175%	$50.5957	$50.60	$50.60	$50.60
Purchase #7	$85.54	9.207%	$93.4157	$93.42	$93.40	$93.40
7 purchase totals =	$1,082.82		$1,176.1588	$1,176.16	$1,176.20	$1,176.10