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	$100.40	3.189%	$103.6018	$103.60	$103.60	$103.60
Purchase #2	$83.66	5.197%	$88.0078	$88.01	$88.00	$88.00
Purchase #3	$155.90	3.128%	$160.7766	$160.78	$160.80	$160.80
Purchase #4	$182.33	9.470%	$199.5967	$199.60	$199.60	$199.60
Purchase #5	$242.48	13.715%	$275.7361	$275.74	$275.75	$275.70
Purchase #6	$153.79	7.718%	$165.6595	$165.66	$165.65	$165.70
Purchase #7	$52.92	3.618%	$54.8346	$54.83	$54.85	$54.80
7 purchase totals =	$971.48		$1,048.2131	$1,048.22	$1,048.25	$1,048.20