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	$248.60	5.332%	$261.8554	$261.86	$261.85	$261.90
Purchase #2	$79.38	11.113%	$88.2015	$88.20	$88.20	$88.20
Purchase #3	$68.95	5.180%	$72.5216	$72.52	$72.50	$72.50
Purchase #4	$58.96	11.115%	$65.5134	$65.51	$65.50	$65.50
Purchase #5	$182.48	5.535%	$192.5803	$192.58	$192.60	$192.60
Purchase #6	$219.47	11.792%	$245.3499	$245.35	$245.35	$245.30
Purchase #7	$55.78	7.358%	$59.8843	$59.88	$59.90	$59.90
7 purchase totals =	$913.62		$985.9064	$985.90	$985.90	$985.90