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	$78.82	9.770%	$86.5207	$86.52	$86.50	$86.50
Purchase #2	$59.93	11.365%	$66.741	$66.74	$66.75	$66.70
Purchase #3	$111.50	6.300%	$118.5245	$118.52	$118.50	$118.50
Purchase #4	$152.37	3.194%	$157.2367	$157.24	$157.25	$157.20
Purchase #5	$179.98	7.411%	$193.3183	$193.32	$193.30	$193.30
Purchase #6	$84.38	8.263%	$91.3523	$91.35	$91.35	$91.40
Purchase #7	$162.55	3.223%	$167.789	$167.79	$167.80	$167.80
7 purchase totals =	$829.53		$881.4825	$881.48	$881.45	$881.40