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	$133.74	6.112%	$141.9142	$141.91	$141.90	$141.90
Purchase #2	$151.69	8.356%	$164.3652	$164.37	$164.35	$164.40
Purchase #3	$96.42	13.314%	$109.2574	$109.26	$109.25	$109.30
Purchase #4	$145.41	4.413%	$151.8269	$151.83	$151.85	$151.80
Purchase #5	$180.71	6.509%	$192.4724	$192.47	$192.45	$192.50
Purchase #6	$12.79	7.138%	$13.703	$13.70	$13.70	$13.70
Purchase #7	$232.74	13.576%	$264.3368	$264.34	$264.35	$264.30
7 purchase totals =	$953.50		$1,037.8759	$1,037.88	$1,037.85	$1,037.90