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	$218.44	7.519%	$234.8645	$234.86	$234.85	$234.90
Purchase #2	$26.35	4.490%	$27.5331	$27.53	$27.55	$27.50
Purchase #3	$129.56	7.168%	$138.8469	$138.85	$138.85	$138.80
Purchase #4	$223.33	8.758%	$242.8892	$242.89	$242.90	$242.90
Purchase #5	$247.59	13.469%	$280.9379	$280.94	$280.95	$280.90
Purchase #6	$39.37	11.453%	$43.879	$43.88	$43.90	$43.90
Purchase #7	$165.60	11.677%	$184.9371	$184.94	$184.95	$184.90
7 purchase totals =	$1,050.24		$1,153.8877	$1,153.89	$1,153.95	$1,153.80