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	$214.67	6.820%	$229.3105	$229.31	$229.30	$229.30
Purchase #2	$171.63	9.109%	$187.2638	$187.26	$187.25	$187.30
Purchase #3	$78.58	4.377%	$82.0194	$82.02	$82.00	$82.00
Purchase #4	$161.27	12.580%	$181.5578	$181.56	$181.55	$181.60
Purchase #5	$149.57	5.772%	$158.2032	$158.20	$158.20	$158.20
Purchase #6	$216.72	5.352%	$228.3189	$228.32	$228.30	$228.30
Purchase #7	$69.46	10.626%	$76.8408	$76.84	$76.85	$76.80
7 purchase totals =	$1,061.90		$1,143.5144	$1,143.51	$1,143.45	$1,143.50