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	$131.89	10.677%	$145.9719	$145.97	$145.95	$146.00
Purchase #2	$211.83	9.156%	$231.2252	$231.23	$231.25	$231.20
Purchase #3	$178.34	7.725%	$192.1168	$192.12	$192.10	$192.10
Purchase #4	$21.58	11.511%	$24.0641	$24.06	$24.05	$24.10
Purchase #5	$189.76	11.182%	$210.979	$210.98	$211.00	$211.00
Purchase #6	$231.28	10.481%	$255.5205	$255.52	$255.50	$255.50
Purchase #7	$147.77	11.430%	$164.6601	$164.66	$164.65	$164.70
7 purchase totals =	$1,112.45		$1,224.5376	$1,224.54	$1,224.50	$1,224.60