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	$52.96	11.483%	$59.0414	$59.04	$59.05	$59.00
Purchase #2	$114.68	5.257%	$120.7087	$120.71	$120.70	$120.70
Purchase #3	$235.48	12.159%	$264.112	$264.11	$264.10	$264.10
Purchase #4	$134.76	10.284%	$148.6187	$148.62	$148.60	$148.60
Purchase #5	$175.30	5.452%	$184.8574	$184.86	$184.85	$184.90
Purchase #6	$176.66	13.492%	$200.495	$200.50	$200.50	$200.50
Purchase #7	$19.34	10.232%	$21.3189	$21.32	$21.30	$21.30
7 purchase totals =	$909.18		$999.1521	$999.16	$999.10	$999.10