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	$194.60	8.599%	$211.3337	$211.33	$211.35	$211.30
Purchase #2	$37.66	13.611%	$42.7859	$42.79	$42.80	$42.80
Purchase #3	$244.62	3.551%	$253.3065	$253.31	$253.30	$253.30
Purchase #4	$97.38	3.511%	$100.799	$100.80	$100.80	$100.80
Purchase #5	$123.83	3.193%	$127.7839	$127.78	$127.80	$127.80
Purchase #6	$112.39	11.125%	$124.8934	$124.89	$124.90	$124.90
Purchase #7	$56.40	4.368%	$58.8636	$58.86	$58.85	$58.90
7 purchase totals =	$866.88		$919.7660	$919.76	$919.80	$919.80