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	$82.46	8.695%	$89.6299	$89.63	$89.65	$89.60
Purchase #2	$75.45	8.808%	$82.0956	$82.10	$82.10	$82.10
Purchase #3	$26.65	6.565%	$28.3996	$28.40	$28.40	$28.40
Purchase #4	$82.96	7.146%	$88.8883	$88.89	$88.90	$88.90
Purchase #5	$52.62	4.618%	$55.05	$55.05	$55.05	$55.10
Purchase #6	$126.72	10.677%	$140.2499	$140.25	$140.25	$140.20
Purchase #7	$33.51	4.389%	$34.9808	$34.98	$35.00	$35.00
7 purchase totals =	$480.37		$519.2941	$519.30	$519.35	$519.30