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	$201.87	4.822%	$211.6042	$211.60	$211.60	$211.60
Purchase #2	$104.43	4.528%	$109.1586	$109.16	$109.15	$109.20
Purchase #3	$129.51	8.485%	$140.4989	$140.50	$140.50	$140.50
Purchase #4	$197.49	6.314%	$209.9595	$209.96	$209.95	$210.00
Purchase #5	$39.59	9.821%	$43.4781	$43.48	$43.50	$43.50
Purchase #6	$20.69	13.791%	$23.5434	$23.54	$23.55	$23.50
Purchase #7	$167.59	13.425%	$190.089	$190.09	$190.10	$190.10
7 purchase totals =	$861.17		$928.3317	$928.33	$928.35	$928.40