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	$221.66	12.499%	$249.3653	$249.37	$249.35	$249.40
Purchase #2	$200.31	11.513%	$223.3717	$223.37	$223.35	$223.40
Purchase #3	$51.46	3.841%	$53.4366	$53.44	$53.45	$53.40
Purchase #4	$79.33	12.453%	$89.209	$89.21	$89.20	$89.20
Purchase #5	$137.65	12.616%	$155.0159	$155.02	$155.00	$155.00
Purchase #6	$195.33	11.837%	$218.4512	$218.45	$218.45	$218.50
Purchase #7	$164.40	7.638%	$176.9569	$176.96	$176.95	$177.00
7 purchase totals =	$1,050.14		$1,165.8066	$1,165.82	$1,165.75	$1,165.90