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	$190.25	3.499%	$196.9068	$196.91	$196.90	$196.90
Purchase #2	$116.73	13.618%	$132.6263	$132.63	$132.65	$132.60
Purchase #3	$140.56	4.292%	$146.5928	$146.59	$146.60	$146.60
Purchase #4	$56.86	10.743%	$62.9685	$62.97	$62.95	$63.00
Purchase #5	$244.61	7.685%	$263.4083	$263.41	$263.40	$263.40
Purchase #6	$109.64	3.130%	$113.0717	$113.07	$113.05	$113.10
Purchase #7	$41.43	9.540%	$45.3824	$45.38	$45.40	$45.40
7 purchase totals =	$900.08		$960.9568	$960.96	$960.95	$961.00