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	$47.74	4.293%	$49.7895	$49.79	$49.80	$49.80
Purchase #2	$79.47	7.582%	$85.4954	$85.50	$85.50	$85.50
Purchase #3	$83.82	6.497%	$89.2658	$89.27	$89.25	$89.30
Purchase #4	$10.43	4.844%	$10.9352	$10.94	$10.95	$10.90
Purchase #5	$42.26	5.158%	$44.4398	$44.44	$44.45	$44.40
Purchase #6	$232.88	12.806%	$262.7026	$262.70	$262.70	$262.70
Purchase #7	$69.29	4.611%	$72.485	$72.49	$72.50	$72.50
7 purchase totals =	$565.89		$615.1133	$615.13	$615.15	$615.10