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	$31.82	10.140%	$35.0465	$35.05	$35.05	$35.00
Purchase #2	$159.91	8.116%	$172.8883	$172.89	$172.90	$172.90
Purchase #3	$145.90	12.571%	$164.2411	$164.24	$164.25	$164.20
Purchase #4	$206.67	9.216%	$225.7167	$225.72	$225.70	$225.70
Purchase #5	$18.55	8.223%	$20.0754	$20.08	$20.10	$20.10
Purchase #6	$91.93	3.598%	$95.2376	$95.24	$95.25	$95.20
Purchase #7	$234.76	8.314%	$254.2779	$254.28	$254.30	$254.30
7 purchase totals =	$889.54		$967.4835	$967.50	$967.55	$967.40