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	$113.56	9.202%	$124.0098	$124.01	$124.00	$124.00
Purchase #2	$215.92	8.216%	$233.66	$233.66	$233.65	$233.70
Purchase #3	$210.67	8.649%	$228.8908	$228.89	$228.90	$228.90
Purchase #4	$107.50	5.326%	$113.2255	$113.23	$113.25	$113.20
Purchase #5	$138.63	6.321%	$147.3928	$147.39	$147.40	$147.40
Purchase #6	$147.66	3.372%	$152.6391	$152.64	$152.65	$152.60
Purchase #7	$176.38	11.212%	$196.1557	$196.16	$196.15	$196.20
7 purchase totals =	$1,110.32		$1,195.9737	$1,195.98	$1,196.00	$1,196.00