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	$134.74	5.523%	$142.1817	$142.18	$142.20	$142.20
Purchase #2	$143.34	3.725%	$148.6794	$148.68	$148.70	$148.70
Purchase #3	$223.91	3.563%	$231.8879	$231.89	$231.90	$231.90
Purchase #4	$128.82	11.812%	$144.0362	$144.04	$144.05	$144.00
Purchase #5	$203.99	3.195%	$210.5075	$210.51	$210.50	$210.50
Purchase #6	$189.67	7.746%	$204.3618	$204.36	$204.35	$204.40
Purchase #7	$41.53	9.617%	$45.5239	$45.52	$45.50	$45.50
7 purchase totals =	$1,066.00		$1,127.1784	$1,127.18	$1,127.20	$1,127.20