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	$167.83	9.686%	$184.086	$184.09	$184.10	$184.10
Purchase #2	$21.58	10.614%	$23.8705	$23.87	$23.85	$23.90
Purchase #3	$96.25	5.248%	$101.3012	$101.30	$101.30	$101.30
Purchase #4	$133.66	4.606%	$139.8164	$139.82	$139.80	$139.80
Purchase #5	$91.89	7.548%	$98.8259	$98.83	$98.85	$98.80
Purchase #6	$86.50	10.188%	$95.3126	$95.31	$95.30	$95.30
Purchase #7	$48.85	11.251%	$54.3461	$54.35	$54.35	$54.30
7 purchase totals =	$646.56		$697.5587	$697.57	$697.55	$697.50