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	$55.79	12.377%	$62.6951	$62.70	$62.70	$62.70
Purchase #2	$190.49	6.803%	$203.449	$203.45	$203.45	$203.40
Purchase #3	$196.29	6.132%	$208.3265	$208.33	$208.35	$208.30
Purchase #4	$128.92	13.152%	$145.8756	$145.88	$145.90	$145.90
Purchase #5	$198.40	12.246%	$222.6961	$222.70	$222.70	$222.70
Purchase #6	$121.27	13.160%	$137.2291	$137.23	$137.25	$137.20
Purchase #7	$51.32	6.773%	$54.7959	$54.80	$54.80	$54.80
7 purchase totals =	$942.48		$1,035.0673	$1,035.09	$1,035.15	$1,035.00