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	$202.37	11.551%	$225.7458	$225.75	$225.75	$225.70
Purchase #2	$183.34	13.518%	$208.1239	$208.12	$208.10	$208.10
Purchase #3	$176.97	6.447%	$188.3793	$188.38	$188.40	$188.40
Purchase #4	$207.61	8.221%	$224.6776	$224.68	$224.70	$224.70
Purchase #5	$105.55	10.476%	$116.6074	$116.61	$116.60	$116.60
Purchase #6	$74.72	10.438%	$82.5193	$82.52	$82.50	$82.50
Purchase #7	$189.71	3.486%	$196.3233	$196.32	$196.30	$196.30
7 purchase totals =	$1,140.27		$1,242.3766	$1,242.38	$1,242.35	$1,242.30