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	$152.52	8.308%	$165.1914	$165.19	$165.20	$165.20
Purchase #2	$36.36	4.530%	$38.0071	$38.01	$38.00	$38.00
Purchase #3	$172.67	9.400%	$188.901	$188.90	$188.90	$188.90
Purchase #4	$40.59	5.774%	$42.9337	$42.93	$42.95	$42.90
Purchase #5	$98.89	11.125%	$109.8915	$109.89	$109.90	$109.90
Purchase #6	$173.93	6.704%	$185.5903	$185.59	$185.60	$185.60
Purchase #7	$109.32	6.748%	$116.6969	$116.70	$116.70	$116.70
7 purchase totals =	$784.28		$847.2119	$847.21	$847.25	$847.20