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	$95.59	6.640%	$101.9372	$101.94	$101.95	$101.90
Purchase #2	$99.83	4.673%	$104.4951	$104.50	$104.50	$104.50
Purchase #3	$18.84	8.797%	$20.4974	$20.50	$20.50	$20.50
Purchase #4	$27.52	8.508%	$29.8614	$29.86	$29.85	$29.90
Purchase #5	$23.61	13.834%	$26.8762	$26.88	$26.90	$26.90
Purchase #6	$81.57	4.416%	$85.1721	$85.17	$85.15	$85.20
Purchase #7	$126.49	13.622%	$143.7205	$143.72	$143.70	$143.70
7 purchase totals =	$473.45		$512.5599	$512.57	$512.55	$512.60