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	$56.55	12.783%	$63.7788	$63.78	$63.80	$63.80
Purchase #2	$104.53	9.496%	$114.4562	$114.46	$114.45	$114.50
Purchase #3	$50.28	4.437%	$52.5109	$52.51	$52.50	$52.50
Purchase #4	$118.41	8.702%	$128.714	$128.71	$128.70	$128.70
Purchase #5	$120.51	5.630%	$127.2947	$127.29	$127.30	$127.30
Purchase #6	$50.39	12.760%	$56.8198	$56.82	$56.80	$56.80
Purchase #7	$60.40	5.587%	$63.7745	$63.77	$63.75	$63.80
7 purchase totals =	$561.07		$607.3489	$607.34	$607.30	$607.40