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	$125.85	11.252%	$140.0106	$140.01	$140.00	$140.00
Purchase #2	$82.40	12.240%	$92.4858	$92.49	$92.50	$92.50
Purchase #3	$226.73	10.347%	$250.1898	$250.19	$250.20	$250.20
Purchase #4	$238.64	8.807%	$259.657	$259.66	$259.65	$259.70
Purchase #5	$45.98	10.761%	$50.9279	$50.93	$50.95	$50.90
Purchase #6	$73.68	6.412%	$78.4044	$78.40	$78.40	$78.40
Purchase #7	$128.38	9.753%	$140.9009	$140.90	$140.90	$140.90
7 purchase totals =	$921.66		$1,012.5764	$1,012.58	$1,012.60	$1,012.60