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	$170.83	4.874%	$179.1563	$179.16	$179.15	$179.20
Purchase #2	$183.78	6.712%	$196.1153	$196.12	$196.10	$196.10
Purchase #3	$39.59	5.261%	$41.6728	$41.67	$41.65	$41.70
Purchase #4	$198.51	5.227%	$208.8861	$208.89	$208.90	$208.90
Purchase #5	$149.62	4.235%	$155.9564	$155.96	$155.95	$156.00
Purchase #6	$139.34	6.528%	$148.4361	$148.44	$148.45	$148.40
Purchase #7	$181.90	10.149%	$200.361	$200.36	$200.35	$200.40
7 purchase totals =	$1,063.57		$1,130.5840	$1,130.60	$1,130.55	$1,130.70