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	$85.89	3.826%	$89.1762	$89.18	$89.20	$89.20
Purchase #2	$176.62	7.815%	$190.4229	$190.42	$190.40	$190.40
Purchase #3	$30.41	7.419%	$32.6661	$32.67	$32.65	$32.70
Purchase #4	$108.97	9.775%	$119.6218	$119.62	$119.60	$119.60
Purchase #5	$48.46	13.421%	$54.9638	$54.96	$54.95	$55.00
Purchase #6	$150.75	3.539%	$156.085	$156.09	$156.10	$156.10
Purchase #7	$155.26	11.502%	$173.118	$173.12	$173.10	$173.10
7 purchase totals =	$756.36		$816.0538	$816.06	$816.00	$816.10