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	$95.54	6.296%	$101.5552	$101.56	$101.55	$101.60
Purchase #2	$45.55	11.567%	$50.8188	$50.82	$50.80	$50.80
Purchase #3	$130.31	6.421%	$138.6772	$138.68	$138.70	$138.70
Purchase #4	$165.25	13.479%	$187.524	$187.52	$187.50	$187.50
Purchase #5	$193.28	13.218%	$218.8278	$218.83	$218.85	$218.80
Purchase #6	$237.77	4.240%	$247.8514	$247.85	$247.85	$247.90
Purchase #7	$59.38	9.278%	$64.8893	$64.89	$64.90	$64.90
7 purchase totals =	$927.08		$1,010.1437	$1,010.15	$1,010.15	$1,010.20