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	$14.98	3.246%	$15.4663	$15.47	$15.45	$15.50
Purchase #2	$54.91	8.798%	$59.741	$59.74	$59.75	$59.70
Purchase #3	$164.89	13.853%	$187.7322	$187.73	$187.75	$187.70
Purchase #4	$89.32	10.624%	$98.8094	$98.81	$98.80	$98.80
Purchase #5	$136.31	11.810%	$152.4082	$152.41	$152.40	$152.40
Purchase #6	$183.90	11.164%	$204.4306	$204.43	$204.45	$204.40
Purchase #7	$42.54	9.636%	$46.6392	$46.64	$46.65	$46.60
7 purchase totals =	$686.85		$765.2269	$765.23	$765.25	$765.10