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	$187.32	4.867%	$196.4369	$196.44	$196.45	$196.40
Purchase #2	$17.59	12.732%	$19.8296	$19.83	$19.85	$19.80
Purchase #3	$245.45	10.632%	$271.5462	$271.55	$271.55	$271.50
Purchase #4	$138.79	8.395%	$150.4414	$150.44	$150.45	$150.40
Purchase #5	$13.38	11.797%	$14.9584	$14.96	$14.95	$15.00
Purchase #6	$63.54	13.841%	$72.3346	$72.33	$72.35	$72.30
Purchase #7	$53.69	7.854%	$57.9068	$57.91	$57.90	$57.90
7 purchase totals =	$719.76		$783.4539	$783.46	$783.50	$783.30