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	$152.64	10.313%	$168.3818	$168.38	$168.40	$168.40
Purchase #2	$112.59	12.684%	$126.8709	$126.87	$126.85	$126.90
Purchase #3	$5.78	9.218%	$6.3128	$6.31	$6.30	$6.30
Purchase #4	$119.42	7.606%	$128.5031	$128.50	$128.50	$128.50
Purchase #5	$19.49	5.838%	$20.6278	$20.63	$20.65	$20.60
Purchase #6	$144.56	8.283%	$156.5339	$156.53	$156.55	$156.50
Purchase #7	$139.56	9.743%	$153.1573	$153.16	$153.15	$153.20
7 purchase totals =	$694.04		$760.3876	$760.38	$760.40	$760.40