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	$53.42	9.438%	$58.4618	$58.46	$58.45	$58.50
Purchase #2	$226.29	11.838%	$253.0782	$253.08	$253.10	$253.10
Purchase #3	$168.85	10.472%	$186.532	$186.53	$186.55	$186.50
Purchase #4	$55.61	6.728%	$59.3514	$59.35	$59.35	$59.40
Purchase #5	$39.81	4.395%	$41.5596	$41.56	$41.55	$41.60
Purchase #6	$111.53	11.718%	$124.5991	$124.60	$124.60	$124.60
Purchase #7	$32.85	11.619%	$36.6668	$36.67	$36.65	$36.70
7 purchase totals =	$688.36		$760.2489	$760.25	$760.25	$760.40