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	$238.79	3.395%	$246.8969	$246.90	$246.90	$246.90
Purchase #2	$232.79	11.660%	$259.9333	$259.93	$259.95	$259.90
Purchase #3	$110.27	13.656%	$125.3285	$125.33	$125.35	$125.30
Purchase #4	$24.55	5.294%	$25.8497	$25.85	$25.85	$25.80
Purchase #5	$112.38	13.408%	$127.4479	$127.45	$127.45	$127.40
Purchase #6	$237.50	7.567%	$255.4716	$255.47	$255.45	$255.50
Purchase #7	$64.84	11.591%	$72.3556	$72.36	$72.35	$72.40
7 purchase totals =	$1,021.12		$1,113.2835	$1,113.29	$1,113.30	$1,113.20