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	$146.27	12.131%	$164.014	$164.01	$164.00	$164.00
Purchase #2	$208.81	3.110%	$215.304	$215.30	$215.30	$215.30
Purchase #3	$80.98	5.311%	$85.2808	$85.28	$85.30	$85.30
Purchase #4	$196.92	7.532%	$211.752	$211.75	$211.75	$211.80
Purchase #5	$136.49	11.656%	$152.3993	$152.40	$152.40	$152.40
Purchase #6	$205.46	13.320%	$232.8273	$232.83	$232.85	$232.80
Purchase #7	$143.69	12.194%	$161.2116	$161.21	$161.20	$161.20
7 purchase totals =	$1,118.62		$1,222.7890	$1,222.78	$1,222.80	$1,222.80