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	$238.33	8.807%	$259.3197	$259.32	$259.30	$259.30
Purchase #2	$92.94	5.442%	$97.9978	$98.00	$98.00	$98.00
Purchase #3	$102.78	5.640%	$108.5768	$108.58	$108.60	$108.60
Purchase #4	$90.29	5.321%	$95.0943	$95.09	$95.10	$95.10
Purchase #5	$172.86	12.293%	$194.1097	$194.11	$194.10	$194.10
Purchase #6	$222.67	12.654%	$250.8467	$250.85	$250.85	$250.80
Purchase #7	$234.79	6.593%	$250.2697	$250.27	$250.25	$250.30
7 purchase totals =	$1,154.66		$1,256.2147	$1,256.22	$1,256.20	$1,256.20