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	$186.46	7.580%	$200.5937	$200.59	$200.60	$200.60
Purchase #2	$159.36	11.737%	$178.0641	$178.06	$178.05	$178.10
Purchase #3	$126.59	4.850%	$132.7296	$132.73	$132.75	$132.70
Purchase #4	$140.85	8.283%	$152.5166	$152.52	$152.50	$152.50
Purchase #5	$119.29	10.420%	$131.72	$131.72	$131.70	$131.70
Purchase #6	$133.40	12.261%	$149.7562	$149.76	$149.75	$149.80
Purchase #7	$164.93	10.677%	$182.5396	$182.54	$182.55	$182.50
7 purchase totals =	$1,030.88		$1,127.9198	$1,127.92	$1,127.90	$1,127.90