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	$180.93	5.165%	$190.275	$190.28	$190.30	$190.30
Purchase #2	$146.84	5.476%	$154.881	$154.88	$154.90	$154.90
Purchase #3	$133.75	5.778%	$141.4781	$141.48	$141.50	$141.50
Purchase #4	$173.77	6.134%	$184.4291	$184.43	$184.45	$184.40
Purchase #5	$219.64	12.864%	$247.8945	$247.89	$247.90	$247.90
Purchase #6	$172.47	3.423%	$178.3736	$178.37	$178.35	$178.40
Purchase #7	$36.35	13.821%	$41.3739	$41.37	$41.35	$41.40
7 purchase totals =	$1,063.75		$1,138.7052	$1,138.70	$1,138.75	$1,138.80