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	$125.25	5.840%	$132.5646	$132.56	$132.55	$132.60
Purchase #2	$234.86	12.796%	$264.9127	$264.91	$264.90	$264.90
Purchase #3	$143.94	4.226%	$150.0229	$150.02	$150.00	$150.00
Purchase #4	$73.58	6.186%	$78.1317	$78.13	$78.15	$78.10
Purchase #5	$59.69	13.714%	$67.8759	$67.88	$67.90	$67.90
Purchase #6	$30.60	3.247%	$31.5936	$31.59	$31.60	$31.60
Purchase #7	$35.28	6.523%	$37.5813	$37.58	$37.60	$37.60
7 purchase totals =	$703.20		$762.6827	$762.67	$762.70	$762.70