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	$182.69	6.365%	$194.3182	$194.32	$194.30	$194.30
Purchase #2	$117.48	6.500%	$125.1162	$125.12	$125.10	$125.10
Purchase #3	$123.63	9.152%	$134.9446	$134.94	$134.95	$134.90
Purchase #4	$90.35	11.200%	$100.4692	$100.47	$100.45	$100.50
Purchase #5	$54.78	7.866%	$59.089	$59.09	$59.10	$59.10
Purchase #6	$141.32	4.430%	$147.5805	$147.58	$147.60	$147.60
Purchase #7	$198.37	12.313%	$222.7953	$222.80	$222.80	$222.80
7 purchase totals =	$908.62		$984.3130	$984.32	$984.30	$984.30