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	$63.66	4.484%	$66.5145	$66.51	$66.50	$66.50
Purchase #2	$133.60	4.287%	$139.3274	$139.33	$139.35	$139.30
Purchase #3	$59.28	4.149%	$61.7395	$61.74	$61.75	$61.70
Purchase #4	$125.55	10.570%	$138.8206	$138.82	$138.80	$138.80
Purchase #5	$183.37	7.126%	$196.4369	$196.44	$196.45	$196.40
Purchase #6	$88.91	13.592%	$100.9946	$100.99	$101.00	$101.00
Purchase #7	$212.32	3.298%	$219.3223	$219.32	$219.30	$219.30
7 purchase totals =	$866.69		$923.1558	$923.15	$923.15	$923.00