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	$182.89	6.403%	$194.6004	$194.60	$194.60	$194.60
Purchase #2	$146.65	11.186%	$163.0543	$163.05	$163.05	$163.10
Purchase #3	$77.72	10.853%	$86.155	$86.16	$86.15	$86.20
Purchase #4	$77.54	6.481%	$82.5654	$82.57	$82.55	$82.60
Purchase #5	$136.64	3.684%	$141.6738	$141.67	$141.65	$141.70
Purchase #6	$86.64	10.219%	$95.4937	$95.49	$95.50	$95.50
Purchase #7	$82.78	12.204%	$92.8825	$92.88	$92.90	$92.90
7 purchase totals =	$790.86		$856.4251	$856.42	$856.40	$856.60