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	$99.48	12.519%	$111.9339	$111.93	$111.95	$111.90
Purchase #2	$183.69	8.195%	$198.7434	$198.74	$198.75	$198.70
Purchase #3	$136.93	10.441%	$151.2269	$151.23	$151.25	$151.20
Purchase #4	$87.30	10.558%	$96.5171	$96.52	$96.50	$96.50
Purchase #5	$134.80	5.747%	$142.547	$142.55	$142.55	$142.50
Purchase #6	$76.72	6.343%	$81.5863	$81.59	$81.60	$81.60
Purchase #7	$177.38	7.616%	$190.8893	$190.89	$190.90	$190.90
7 purchase totals =	$896.30		$973.4439	$973.45	$973.50	$973.30