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	$212.77	13.804%	$242.1408	$242.14	$242.15	$242.10
Purchase #2	$28.44	13.620%	$32.3135	$32.31	$32.30	$32.30
Purchase #3	$179.56	5.430%	$189.3101	$189.31	$189.30	$189.30
Purchase #4	$217.37	6.285%	$231.0317	$231.03	$231.05	$231.00
Purchase #5	$93.45	6.454%	$99.4813	$99.48	$99.50	$99.50
Purchase #6	$32.80	6.869%	$35.053	$35.05	$35.05	$35.10
Purchase #7	$118.75	12.435%	$133.5166	$133.52	$133.50	$133.50
7 purchase totals =	$883.14		$962.8470	$962.84	$962.85	$962.80