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	$36.51	13.313%	$41.3706	$41.37	$41.35	$41.40
Purchase #2	$185.78	4.557%	$194.246	$194.25	$194.25	$194.20
Purchase #3	$73.56	6.654%	$78.4547	$78.45	$78.45	$78.50
Purchase #4	$71.31	9.413%	$78.0224	$78.02	$78.00	$78.00
Purchase #5	$246.58	5.815%	$260.9186	$260.92	$260.90	$260.90
Purchase #6	$133.31	13.145%	$150.8336	$150.83	$150.85	$150.80
Purchase #7	$85.36	8.429%	$92.555	$92.56	$92.55	$92.60
7 purchase totals =	$832.41		$896.4009	$896.40	$896.35	$896.40