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	$73.47	3.367%	$75.9437	$75.94	$75.95	$75.90
Purchase #2	$124.60	13.165%	$141.0036	$141.00	$141.00	$141.00
Purchase #3	$66.47	8.316%	$71.9976	$72.00	$72.00	$72.00
Purchase #4	$205.47	12.834%	$231.84	$231.84	$231.85	$231.80
Purchase #5	$79.37	12.240%	$89.0849	$89.08	$89.10	$89.10
Purchase #6	$71.87	12.142%	$80.5965	$80.60	$80.60	$80.60
Purchase #7	$155.71	11.503%	$173.6213	$173.62	$173.60	$173.60
7 purchase totals =	$776.96		$864.0876	$864.08	$864.10	$864.00