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	$189.58	8.873%	$206.4014	$206.40	$206.40	$206.40
Purchase #2	$162.47	3.550%	$168.2377	$168.24	$168.25	$168.20
Purchase #3	$217.45	4.703%	$227.6767	$227.68	$227.70	$227.70
Purchase #4	$67.91	6.541%	$72.352	$72.35	$72.35	$72.40
Purchase #5	$197.33	4.310%	$205.8349	$205.83	$205.85	$205.80
Purchase #6	$238.32	3.186%	$245.9129	$245.91	$245.90	$245.90
Purchase #7	$72.37	13.832%	$82.3802	$82.38	$82.40	$82.40
7 purchase totals =	$1,145.43		$1,208.7958	$1,208.79	$1,208.85	$1,208.80