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	$246.98	13.742%	$280.92	$280.92	$280.90	$280.90
Purchase #2	$42.61	6.226%	$45.2629	$45.26	$45.25	$45.30
Purchase #3	$241.93	6.453%	$257.5417	$257.54	$257.55	$257.50
Purchase #4	$150.71	5.547%	$159.0699	$159.07	$159.05	$159.10
Purchase #5	$140.98	13.847%	$160.5015	$160.50	$160.50	$160.50
Purchase #6	$124.34	13.670%	$141.3373	$141.34	$141.35	$141.30
Purchase #7	$158.84	6.222%	$168.723	$168.72	$168.70	$168.70
7 purchase totals =	$1,106.39		$1,213.3563	$1,213.35	$1,213.30	$1,213.30