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	$48.72	7.565%	$52.4057	$52.41	$52.40	$52.40
Purchase #2	$35.73	3.608%	$37.0191	$37.02	$37.00	$37.00
Purchase #3	$54.76	8.412%	$59.3664	$59.37	$59.35	$59.40
Purchase #4	$12.53	13.613%	$14.2357	$14.24	$14.25	$14.20
Purchase #5	$37.55	5.166%	$39.4898	$39.49	$39.50	$39.50
Purchase #6	$224.83	3.443%	$232.5709	$232.57	$232.55	$232.60
Purchase #7	$173.57	3.297%	$179.2926	$179.29	$179.30	$179.30
7 purchase totals =	$587.69		$614.3802	$614.39	$614.35	$614.40