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	$99.51	5.413%	$104.8965	$104.90	$104.90	$104.90
Purchase #2	$89.82	10.116%	$98.9062	$98.91	$98.90	$98.90
Purchase #3	$30.91	4.776%	$32.3863	$32.39	$32.40	$32.40
Purchase #4	$152.99	7.803%	$164.9278	$164.93	$164.95	$164.90
Purchase #5	$198.44	12.324%	$222.8957	$222.90	$222.90	$222.90
Purchase #6	$165.93	8.663%	$180.3045	$180.30	$180.30	$180.30
Purchase #7	$228.59	3.851%	$237.393	$237.39	$237.40	$237.40
7 purchase totals =	$966.19		$1,041.7100	$1,041.72	$1,041.75	$1,041.70