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	$168.98	9.628%	$185.2494	$185.25	$185.25	$185.20
Purchase #2	$27.89	7.124%	$29.8769	$29.88	$29.90	$29.90
Purchase #3	$98.70	8.865%	$107.4498	$107.45	$107.45	$107.40
Purchase #4	$162.78	10.807%	$180.3716	$180.37	$180.35	$180.40
Purchase #5	$67.67	12.247%	$75.9575	$75.96	$75.95	$76.00
Purchase #6	$53.85	10.238%	$59.3632	$59.36	$59.35	$59.40
Purchase #7	$9.75	5.198%	$10.2568	$10.26	$10.25	$10.30
7 purchase totals =	$589.62		$648.5252	$648.53	$648.50	$648.60