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	$112.74	5.243%	$118.651	$118.65	$118.65	$118.70
Purchase #2	$123.39	13.872%	$140.5067	$140.51	$140.50	$140.50
Purchase #3	$179.66	13.670%	$204.2195	$204.22	$204.20	$204.20
Purchase #4	$59.54	13.156%	$67.3731	$67.37	$67.35	$67.40
Purchase #5	$110.91	11.311%	$123.455	$123.46	$123.45	$123.50
Purchase #6	$103.58	12.290%	$116.31	$116.31	$116.30	$116.30
Purchase #7	$30.79	8.181%	$33.3089	$33.31	$33.30	$33.30
7 purchase totals =	$720.61		$803.8242	$803.83	$803.75	$803.90