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	$38.44	10.813%	$42.5965	$42.60	$42.60	$42.60
Purchase #2	$59.57	13.530%	$67.6298	$67.63	$67.65	$67.60
Purchase #3	$100.68	11.473%	$112.231	$112.23	$112.25	$112.20
Purchase #4	$87.88	8.438%	$95.2953	$95.30	$95.30	$95.30
Purchase #5	$194.58	12.691%	$219.2741	$219.27	$219.25	$219.30
Purchase #6	$97.54	10.832%	$108.1055	$108.11	$108.10	$108.10
Purchase #7	$9.79	11.142%	$10.8808	$10.88	$10.90	$10.90
7 purchase totals =	$588.48		$656.0130	$656.02	$656.05	$656.00