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	$190.35	10.697%	$210.7117	$210.71	$210.70	$210.70
Purchase #2	$201.82	10.102%	$222.2079	$222.21	$222.20	$222.20
Purchase #3	$17.30	5.521%	$18.2551	$18.26	$18.25	$18.30
Purchase #4	$195.32	12.259%	$219.2643	$219.26	$219.25	$219.30
Purchase #5	$208.70	6.376%	$222.0067	$222.01	$222.00	$222.00
Purchase #6	$92.41	8.268%	$100.0505	$100.05	$100.05	$100.10
Purchase #7	$139.85	6.871%	$149.4591	$149.46	$149.45	$149.50
7 purchase totals =	$1,045.75		$1,141.9553	$1,141.96	$1,141.90	$1,142.10