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	$191.29	6.359%	$203.4541	$203.45	$203.45	$203.50
Purchase #2	$196.29	13.700%	$223.1817	$223.18	$223.20	$223.20
Purchase #3	$101.73	9.568%	$111.4635	$111.46	$111.45	$111.50
Purchase #4	$83.46	7.347%	$89.5918	$89.59	$89.60	$89.60
Purchase #5	$190.63	13.612%	$216.5786	$216.58	$216.60	$216.60
Purchase #6	$158.57	10.112%	$174.6046	$174.60	$174.60	$174.60
Purchase #7	$36.55	11.132%	$40.6187	$40.62	$40.60	$40.60
7 purchase totals =	$958.52		$1,059.4930	$1,059.48	$1,059.50	$1,059.60