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	$242.38	9.322%	$264.9747	$264.97	$264.95	$265.00
Purchase #2	$43.56	7.663%	$46.898	$46.90	$46.90	$46.90
Purchase #3	$145.61	12.706%	$164.1112	$164.11	$164.10	$164.10
Purchase #4	$18.59	10.128%	$20.4728	$20.47	$20.45	$20.50
Purchase #5	$94.77	4.776%	$99.2962	$99.30	$99.30	$99.30
Purchase #6	$136.34	3.500%	$141.1119	$141.11	$141.10	$141.10
Purchase #7	$137.96	6.104%	$146.3811	$146.38	$146.40	$146.40
7 purchase totals =	$819.21		$883.2459	$883.24	$883.20	$883.30