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	$41.89	3.499%	$43.3557	$43.36	$43.35	$43.40
Purchase #2	$97.32	10.820%	$107.85	$107.85	$107.85	$107.90
Purchase #3	$195.75	13.608%	$222.3877	$222.39	$222.40	$222.40
Purchase #4	$222.39	8.387%	$241.0418	$241.04	$241.05	$241.00
Purchase #5	$115.62	10.739%	$128.0364	$128.04	$128.05	$128.00
Purchase #6	$134.40	10.282%	$148.219	$148.22	$148.20	$148.20
Purchase #7	$141.74	5.837%	$150.0134	$150.01	$150.00	$150.00
7 purchase totals =	$949.11		$1,040.9040	$1,040.91	$1,040.90	$1,040.90