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	$142.46	13.751%	$162.0497	$162.05	$162.05	$162.00
Purchase #2	$141.30	11.718%	$157.8575	$157.86	$157.85	$157.90
Purchase #3	$89.55	12.436%	$100.6864	$100.69	$100.70	$100.70
Purchase #4	$76.31	8.551%	$82.8353	$82.84	$82.85	$82.80
Purchase #5	$142.73	3.481%	$147.6984	$147.70	$147.70	$147.70
Purchase #6	$39.67	13.530%	$45.0374	$45.04	$45.05	$45.00
Purchase #7	$114.93	3.229%	$118.6411	$118.64	$118.65	$118.60
7 purchase totals =	$746.95		$814.8058	$814.82	$814.85	$814.70