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	$136.34	6.784%	$145.5893	$145.59	$145.60	$145.60
Purchase #2	$40.26	6.422%	$42.8455	$42.85	$42.85	$42.80
Purchase #3	$126.37	11.693%	$141.1464	$141.15	$141.15	$141.10
Purchase #4	$183.98	11.450%	$205.0457	$205.05	$205.05	$205.00
Purchase #5	$144.34	5.590%	$152.4086	$152.41	$152.40	$152.40
Purchase #6	$250.47	8.234%	$271.0937	$271.09	$271.10	$271.10
Purchase #7	$77.74	3.152%	$80.1904	$80.19	$80.20	$80.20
7 purchase totals =	$959.50		$1,038.3196	$1,038.33	$1,038.35	$1,038.20