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	$101.50	3.374%	$104.9246	$104.92	$104.90	$104.90
Purchase #2	$233.99	11.168%	$260.122	$260.12	$260.10	$260.10
Purchase #3	$211.43	10.171%	$232.9345	$232.93	$232.95	$232.90
Purchase #4	$207.82	8.693%	$225.8858	$225.89	$225.90	$225.90
Purchase #5	$243.88	4.284%	$254.3278	$254.33	$254.35	$254.30
Purchase #6	$90.67	10.857%	$100.514	$100.51	$100.50	$100.50
Purchase #7	$35.67	13.591%	$40.5179	$40.52	$40.50	$40.50
7 purchase totals =	$1,124.96		$1,219.2266	$1,219.22	$1,219.20	$1,219.10