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	$39.40	5.236%	$41.463	$41.46	$41.45	$41.50
Purchase #2	$150.36	13.748%	$171.0315	$171.03	$171.05	$171.00
Purchase #3	$108.79	8.706%	$118.2613	$118.26	$118.25	$118.30
Purchase #4	$102.74	6.748%	$109.6729	$109.67	$109.65	$109.70
Purchase #5	$193.30	3.646%	$200.3477	$200.35	$200.35	$200.30
Purchase #6	$45.67	13.468%	$51.8208	$51.82	$51.80	$51.80
Purchase #7	$167.74	13.346%	$190.1266	$190.13	$190.15	$190.10
7 purchase totals =	$808.00		$882.7238	$882.72	$882.70	$882.70