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	$199.89	11.236%	$222.3496	$222.35	$222.35	$222.30
Purchase #2	$150.32	5.779%	$159.007	$159.01	$159.00	$159.00
Purchase #3	$173.37	7.552%	$186.4629	$186.46	$186.45	$186.50
Purchase #4	$16.80	11.680%	$18.7622	$18.76	$18.75	$18.80
Purchase #5	$141.98	10.291%	$156.5912	$156.59	$156.60	$156.60
Purchase #6	$214.89	13.270%	$243.4059	$243.41	$243.40	$243.40
Purchase #7	$106.53	9.839%	$117.0115	$117.01	$117.00	$117.00
7 purchase totals =	$1,003.78		$1,103.5903	$1,103.59	$1,103.55	$1,103.60