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	$108.90	9.776%	$119.5461	$119.55	$119.55	$119.50
Purchase #2	$79.61	3.857%	$82.6806	$82.68	$82.70	$82.70
Purchase #3	$88.35	12.581%	$99.4653	$99.47	$99.45	$99.50
Purchase #4	$77.32	3.825%	$80.2775	$80.28	$80.30	$80.30
Purchase #5	$141.77	7.227%	$152.0157	$152.02	$152.00	$152.00
Purchase #6	$48.54	5.282%	$51.1039	$51.10	$51.10	$51.10
Purchase #7	$176.96	4.280%	$184.5339	$184.53	$184.55	$184.50
7 purchase totals =	$721.45		$769.6230	$769.63	$769.65	$769.60