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	$98.81	11.672%	$110.3431	$110.34	$110.35	$110.30
Purchase #2	$137.90	10.800%	$152.7932	$152.79	$152.80	$152.80
Purchase #3	$127.27	12.475%	$143.1469	$143.15	$143.15	$143.10
Purchase #4	$31.85	11.613%	$35.5487	$35.55	$35.55	$35.50
Purchase #5	$216.43	7.725%	$233.1492	$233.15	$233.15	$233.10
Purchase #6	$250.73	6.422%	$266.8319	$266.83	$266.85	$266.80
Purchase #7	$72.44	9.382%	$79.2363	$79.24	$79.25	$79.20
7 purchase totals =	$935.43		$1,021.0493	$1,021.05	$1,021.10	$1,020.80