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	$179.66	5.802%	$190.0839	$190.08	$190.10	$190.10
Purchase #2	$30.73	5.475%	$32.4125	$32.41	$32.40	$32.40
Purchase #3	$38.41	3.818%	$39.8765	$39.88	$39.90	$39.90
Purchase #4	$10.54	12.621%	$11.8703	$11.87	$11.85	$11.90
Purchase #5	$168.40	8.759%	$183.1502	$183.15	$183.15	$183.20
Purchase #6	$79.43	13.651%	$90.273	$90.27	$90.25	$90.30
Purchase #7	$129.85	6.367%	$138.1175	$138.12	$138.10	$138.10
7 purchase totals =	$637.02		$685.7839	$685.78	$685.75	$685.90