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	$168.90	13.466%	$191.6441	$191.64	$191.65	$191.60
Purchase #2	$92.58	13.427%	$105.0107	$105.01	$105.00	$105.00
Purchase #3	$58.58	11.746%	$65.4608	$65.46	$65.45	$65.50
Purchase #4	$49.27	11.776%	$55.072	$55.07	$55.05	$55.10
Purchase #5	$57.87	4.616%	$60.5413	$60.54	$60.55	$60.50
Purchase #6	$158.96	3.220%	$164.0785	$164.08	$164.10	$164.10
Purchase #7	$141.57	11.285%	$157.5462	$157.55	$157.55	$157.50
7 purchase totals =	$727.73		$799.3536	$799.35	$799.35	$799.30