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	$250.56	6.316%	$266.3854	$266.39	$266.40	$266.40
Purchase #2	$94.32	6.385%	$100.3423	$100.34	$100.35	$100.30
Purchase #3	$113.52	3.463%	$117.4512	$117.45	$117.45	$117.50
Purchase #4	$42.92	6.644%	$45.7716	$45.77	$45.75	$45.80
Purchase #5	$233.88	4.785%	$245.0712	$245.07	$245.05	$245.10
Purchase #6	$88.67	6.209%	$94.1755	$94.18	$94.20	$94.20
Purchase #7	$187.33	8.483%	$203.2212	$203.22	$203.20	$203.20
7 purchase totals =	$1,011.20		$1,072.4184	$1,072.42	$1,072.40	$1,072.50