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	$198.79	5.306%	$209.3378	$209.34	$209.35	$209.30
Purchase #2	$45.48	10.529%	$50.2686	$50.27	$50.25	$50.30
Purchase #3	$71.68	5.509%	$75.6289	$75.63	$75.65	$75.60
Purchase #4	$58.90	11.167%	$65.4774	$65.48	$65.50	$65.50
Purchase #5	$214.94	3.863%	$223.2431	$223.24	$223.25	$223.20
Purchase #6	$69.27	13.376%	$78.5356	$78.54	$78.55	$78.50
Purchase #7	$82.69	10.629%	$91.4791	$91.48	$91.50	$91.50
7 purchase totals =	$741.75		$793.9705	$793.98	$794.05	$793.90