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	$115.28	7.250%	$123.6378	$123.64	$123.65	$123.60
Purchase #2	$244.67	7.214%	$262.3205	$262.32	$262.30	$262.30
Purchase #3	$181.32	9.756%	$199.0096	$199.01	$199.00	$199.00
Purchase #4	$160.76	13.780%	$182.9127	$182.91	$182.90	$182.90
Purchase #5	$124.50	9.304%	$136.0835	$136.08	$136.10	$136.10
Purchase #6	$147.29	12.711%	$166.012	$166.01	$166.00	$166.00
Purchase #7	$41.96	3.369%	$43.3736	$43.37	$43.35	$43.40
7 purchase totals =	$1,015.78		$1,113.3497	$1,113.34	$1,113.30	$1,113.30