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	$103.74	6.571%	$110.5568	$110.56	$110.55	$110.60
Purchase #2	$178.65	7.820%	$192.6204	$192.62	$192.60	$192.60
Purchase #3	$242.66	12.197%	$272.2572	$272.26	$272.25	$272.30
Purchase #4	$130.25	10.276%	$143.6345	$143.63	$143.65	$143.60
Purchase #5	$81.90	5.700%	$86.5683	$86.57	$86.55	$86.60
Purchase #6	$68.62	5.402%	$72.3269	$72.33	$72.35	$72.30
Purchase #7	$127.83	12.108%	$143.3077	$143.31	$143.30	$143.30
7 purchase totals =	$933.65		$1,021.2718	$1,021.28	$1,021.25	$1,021.30