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	$80.92	5.596%	$85.4483	$85.45	$85.45	$85.40
Purchase #2	$157.67	7.584%	$169.6277	$169.63	$169.65	$169.60
Purchase #3	$43.46	6.684%	$46.3649	$46.36	$46.35	$46.40
Purchase #4	$137.71	10.597%	$152.3031	$152.30	$152.30	$152.30
Purchase #5	$72.70	13.552%	$82.5523	$82.55	$82.55	$82.60
Purchase #6	$118.81	8.275%	$128.6415	$128.64	$128.65	$128.60
Purchase #7	$56.57	5.435%	$59.6446	$59.64	$59.65	$59.60
7 purchase totals =	$667.84		$724.5824	$724.57	$724.60	$724.50