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	$118.41	4.288%	$123.4874	$123.49	$123.50	$123.50
Purchase #2	$42.83	13.633%	$48.669	$48.67	$48.65	$48.70
Purchase #3	$10.77	6.784%	$11.5006	$11.50	$11.50	$11.50
Purchase #4	$30.67	12.497%	$34.5028	$34.50	$34.50	$34.50
Purchase #5	$148.77	9.216%	$162.4806	$162.48	$162.50	$162.50
Purchase #6	$222.53	9.587%	$243.864	$243.86	$243.85	$243.90
Purchase #7	$67.46	12.752%	$76.0625	$76.06	$76.05	$76.10
7 purchase totals =	$641.44		$700.5669	$700.56	$700.55	$700.70