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	$189.27	4.867%	$198.4818	$198.48	$198.50	$198.50
Purchase #2	$209.55	11.716%	$234.1009	$234.10	$234.10	$234.10
Purchase #3	$31.77	4.742%	$33.2765	$33.28	$33.30	$33.30
Purchase #4	$246.33	11.434%	$274.4954	$274.50	$274.50	$274.50
Purchase #5	$151.77	8.605%	$164.8298	$164.83	$164.85	$164.80
Purchase #6	$77.66	6.418%	$82.6442	$82.64	$82.65	$82.60
Purchase #7	$167.37	5.561%	$176.6774	$176.68	$176.70	$176.70
7 purchase totals =	$1,073.72		$1,164.5060	$1,164.51	$1,164.60	$1,164.50