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	$95.46	13.544%	$108.3891	$108.39	$108.40	$108.40
Purchase #2	$185.38	5.482%	$195.5425	$195.54	$195.55	$195.50
Purchase #3	$139.72	6.256%	$148.4609	$148.46	$148.45	$148.50
Purchase #4	$116.89	4.869%	$122.5814	$122.58	$122.60	$122.60
Purchase #5	$165.58	13.231%	$187.4879	$187.49	$187.50	$187.50
Purchase #6	$188.53	3.179%	$194.5234	$194.52	$194.50	$194.50
Purchase #7	$45.26	13.141%	$51.2076	$51.21	$51.20	$51.20
7 purchase totals =	$936.82		$1,008.1928	$1,008.19	$1,008.20	$1,008.20