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	$112.95	4.689%	$118.2462	$118.25	$118.25	$118.20
Purchase #2	$48.34	12.274%	$54.2733	$54.27	$54.25	$54.30
Purchase #3	$242.88	7.152%	$260.2508	$260.25	$260.25	$260.30
Purchase #4	$202.51	5.610%	$213.8708	$213.87	$213.85	$213.90
Purchase #5	$59.28	5.237%	$62.3845	$62.38	$62.40	$62.40
Purchase #6	$149.98	12.361%	$168.519	$168.52	$168.50	$168.50
Purchase #7	$59.86	7.678%	$64.4561	$64.46	$64.45	$64.50
7 purchase totals =	$875.80		$942.0007	$942.00	$941.95	$942.10