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	$157.29	4.160%	$163.8333	$163.83	$163.85	$163.80
Purchase #2	$96.37	3.413%	$99.6591	$99.66	$99.65	$99.70
Purchase #3	$134.45	9.711%	$147.5064	$147.51	$147.50	$147.50
Purchase #4	$40.75	5.256%	$42.8918	$42.89	$42.90	$42.90
Purchase #5	$11.31	3.753%	$11.7345	$11.73	$11.75	$11.70
Purchase #6	$206.86	5.133%	$217.4781	$217.48	$217.50	$217.50
Purchase #7	$136.73	3.403%	$141.3829	$141.38	$141.40	$141.40
7 purchase totals =	$783.76		$824.4861	$824.48	$824.55	$824.50