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	$148.92	9.192%	$162.6087	$162.61	$162.60	$162.60
Purchase #2	$72.92	4.513%	$76.2109	$76.21	$76.20	$76.20
Purchase #3	$190.76	10.361%	$210.5246	$210.52	$210.50	$210.50
Purchase #4	$135.66	11.253%	$150.9258	$150.93	$150.95	$150.90
Purchase #5	$5.58	13.522%	$6.3345	$6.33	$6.35	$6.30
Purchase #6	$223.66	7.854%	$241.2263	$241.23	$241.25	$241.20
Purchase #7	$210.97	13.245%	$238.913	$238.91	$238.90	$238.90
7 purchase totals =	$988.47		$1,086.7438	$1,086.74	$1,086.75	$1,086.60