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	$76.85	5.376%	$80.9815	$80.98	$81.00	$81.00
Purchase #2	$168.91	4.343%	$176.2458	$176.25	$176.25	$176.20
Purchase #3	$156.61	3.601%	$162.2495	$162.25	$162.25	$162.20
Purchase #4	$150.88	5.327%	$158.9174	$158.92	$158.90	$158.90
Purchase #5	$44.45	11.386%	$49.5111	$49.51	$49.50	$49.50
Purchase #6	$159.25	5.253%	$167.6154	$167.62	$167.60	$167.60
Purchase #7	$94.39	5.748%	$99.8155	$99.82	$99.80	$99.80
7 purchase totals =	$851.34		$895.3362	$895.35	$895.30	$895.20