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	$241.93	7.444%	$259.9393	$259.94	$259.95	$259.90
Purchase #2	$229.47	11.627%	$256.1505	$256.15	$256.15	$256.20
Purchase #3	$238.79	13.579%	$271.2153	$271.22	$271.20	$271.20
Purchase #4	$6.57	6.497%	$6.9969	$7.00	$7.00	$7.00
Purchase #5	$177.60	10.796%	$196.7737	$196.77	$196.75	$196.80
Purchase #6	$10.49	8.824%	$11.4156	$11.42	$11.40	$11.40
Purchase #7	$223.92	7.356%	$240.3916	$240.39	$240.40	$240.40
7 purchase totals =	$1,128.77		$1,242.8829	$1,242.89	$1,242.85	$1,242.90