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	$142.97	5.158%	$150.3444	$150.34	$150.35	$150.30
Purchase #2	$151.36	5.566%	$159.7847	$159.78	$159.80	$159.80
Purchase #3	$35.80	5.673%	$37.8309	$37.83	$37.85	$37.80
Purchase #4	$137.66	11.534%	$153.5377	$153.54	$153.55	$153.50
Purchase #5	$174.90	9.470%	$191.463	$191.46	$191.45	$191.50
Purchase #6	$229.41	4.110%	$238.8388	$238.84	$238.85	$238.80
Purchase #7	$127.84	7.201%	$137.0458	$137.05	$137.05	$137.00
7 purchase totals =	$999.94		$1,068.8453	$1,068.84	$1,068.90	$1,068.70