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	$99.89	3.623%	$103.509	$103.51	$103.50	$103.50
Purchase #2	$234.92	12.484%	$264.2474	$264.25	$264.25	$264.20
Purchase #3	$82.39	7.231%	$88.3476	$88.35	$88.35	$88.30
Purchase #4	$108.47	3.235%	$111.979	$111.98	$112.00	$112.00
Purchase #5	$179.85	11.245%	$200.0741	$200.07	$200.05	$200.10
Purchase #6	$161.25	4.794%	$168.9803	$168.98	$169.00	$169.00
Purchase #7	$203.59	9.498%	$222.927	$222.93	$222.95	$222.90
7 purchase totals =	$1,070.36		$1,160.0644	$1,160.07	$1,160.10	$1,160.00