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	$103.50	10.482%	$114.3489	$114.35	$114.35	$114.30
Purchase #2	$33.47	4.814%	$35.0812	$35.08	$35.10	$35.10
Purchase #3	$136.30	8.382%	$147.7247	$147.72	$147.70	$147.70
Purchase #4	$17.33	4.706%	$18.1455	$18.15	$18.15	$18.10
Purchase #5	$94.98	10.256%	$104.7211	$104.72	$104.70	$104.70
Purchase #6	$138.93	12.213%	$155.8975	$155.90	$155.90	$155.90
Purchase #7	$202.36	10.484%	$223.5754	$223.58	$223.60	$223.60
7 purchase totals =	$726.87		$799.4943	$799.50	$799.50	$799.40