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	$153.81	9.507%	$168.4327	$168.43	$168.45	$168.40
Purchase #2	$34.94	7.709%	$37.6335	$37.63	$37.65	$37.60
Purchase #3	$156.92	3.567%	$162.5173	$162.52	$162.50	$162.50
Purchase #4	$30.49	4.472%	$31.8535	$31.85	$31.85	$31.90
Purchase #5	$149.58	3.312%	$154.5341	$154.53	$154.55	$154.50
Purchase #6	$48.30	4.529%	$50.4875	$50.49	$50.50	$50.50
Purchase #7	$6.39	9.250%	$6.9811	$6.98	$7.00	$7.00
7 purchase totals =	$580.43		$612.4397	$612.43	$612.50	$612.40