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	$134.65	6.612%	$143.5531	$143.55	$143.55	$143.60
Purchase #2	$208.31	3.392%	$215.3759	$215.38	$215.40	$215.40
Purchase #3	$84.83	7.462%	$91.16	$91.16	$91.15	$91.20
Purchase #4	$180.26	13.485%	$204.5681	$204.57	$204.55	$204.60
Purchase #5	$164.83	13.405%	$186.9255	$186.93	$186.95	$186.90
Purchase #6	$111.55	7.576%	$120.001	$120.00	$120.00	$120.00
Purchase #7	$42.26	8.183%	$45.7181	$45.72	$45.70	$45.70
7 purchase totals =	$926.69		$1,007.3017	$1,007.31	$1,007.30	$1,007.40