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	$22.94	7.633%	$24.691	$24.69	$24.70	$24.70
Purchase #2	$97.51	6.220%	$103.5751	$103.58	$103.60	$103.60
Purchase #3	$64.85	3.359%	$67.0283	$67.03	$67.05	$67.00
Purchase #4	$99.53	12.404%	$111.8757	$111.88	$111.90	$111.90
Purchase #5	$85.48	3.657%	$88.606	$88.61	$88.60	$88.60
Purchase #6	$157.63	13.563%	$179.0094	$179.01	$179.00	$179.00
Purchase #7	$198.49	3.862%	$206.1557	$206.16	$206.15	$206.20
7 purchase totals =	$726.43		$780.9412	$780.96	$781.00	$781.00