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	$78.67	4.860%	$82.4934	$82.49	$82.50	$82.50
Purchase #2	$11.41	10.347%	$12.5906	$12.59	$12.60	$12.60
Purchase #3	$226.59	3.300%	$234.0675	$234.07	$234.05	$234.10
Purchase #4	$62.44	4.134%	$65.0213	$65.02	$65.00	$65.00
Purchase #5	$113.25	7.665%	$121.9306	$121.93	$121.95	$121.90
Purchase #6	$162.72	3.304%	$168.0963	$168.10	$168.10	$168.10
Purchase #7	$125.86	4.557%	$131.5954	$131.60	$131.60	$131.60
7 purchase totals =	$780.94		$815.7951	$815.80	$815.80	$815.80