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	$144.91	5.787%	$153.2959	$153.30	$153.30	$153.30
Purchase #2	$57.82	8.162%	$62.5393	$62.54	$62.55	$62.50
Purchase #3	$95.85	9.614%	$105.065	$105.07	$105.05	$105.10
Purchase #4	$112.81	5.516%	$119.0326	$119.03	$119.05	$119.00
Purchase #5	$209.96	11.169%	$233.4104	$233.41	$233.40	$233.40
Purchase #6	$16.67	12.225%	$18.7079	$18.71	$18.70	$18.70
Purchase #7	$43.26	5.182%	$45.5017	$45.50	$45.50	$45.50
7 purchase totals =	$681.28		$737.5528	$737.56	$737.55	$737.50