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	$133.37	7.852%	$143.8422	$143.84	$143.85	$143.80
Purchase #2	$236.84	10.127%	$260.8248	$260.82	$260.80	$260.80
Purchase #3	$6.83	5.347%	$7.1952	$7.20	$7.20	$7.20
Purchase #4	$204.53	3.818%	$212.339	$212.34	$212.35	$212.30
Purchase #5	$140.35	11.509%	$156.5029	$156.50	$156.50	$156.50
Purchase #6	$75.98	4.300%	$79.2471	$79.25	$79.25	$79.20
Purchase #7	$127.86	11.373%	$142.4015	$142.40	$142.40	$142.40
7 purchase totals =	$925.76		$1,002.3527	$1,002.35	$1,002.35	$1,002.20