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	$203.94	9.183%	$222.6678	$222.67	$222.65	$222.70
Purchase #2	$219.47	4.234%	$228.7624	$228.76	$228.75	$228.80
Purchase #3	$30.51	8.252%	$33.0277	$33.03	$33.05	$33.00
Purchase #4	$97.90	5.685%	$103.4656	$103.47	$103.45	$103.50
Purchase #5	$80.51	3.488%	$83.3182	$83.32	$83.30	$83.30
Purchase #6	$199.69	11.567%	$222.7881	$222.79	$222.80	$222.80
Purchase #7	$190.77	10.820%	$211.4113	$211.41	$211.40	$211.40
7 purchase totals =	$1,022.79		$1,105.4411	$1,105.45	$1,105.40	$1,105.50