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	$146.47	8.466%	$158.8702	$158.87	$158.85	$158.90
Purchase #2	$115.85	8.873%	$126.1294	$126.13	$126.15	$126.10
Purchase #3	$248.90	11.505%	$277.5359	$277.54	$277.55	$277.50
Purchase #4	$56.26	5.674%	$59.4522	$59.45	$59.45	$59.50
Purchase #5	$132.61	8.859%	$144.3579	$144.36	$144.35	$144.40
Purchase #6	$207.96	5.257%	$218.8925	$218.89	$218.90	$218.90
Purchase #7	$132.55	6.197%	$140.7641	$140.76	$140.75	$140.80
7 purchase totals =	$1,040.60		$1,126.0022	$1,126.00	$1,126.00	$1,126.10