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	$200.79	6.274%	$213.3876	$213.39	$213.40	$213.40
Purchase #2	$80.38	4.284%	$83.8235	$83.82	$83.80	$83.80
Purchase #3	$249.86	5.113%	$262.6353	$262.64	$262.65	$262.60
Purchase #4	$130.87	6.768%	$139.7273	$139.73	$139.75	$139.70
Purchase #5	$68.65	3.111%	$70.7857	$70.79	$70.80	$70.80
Purchase #6	$7.39	6.706%	$7.8856	$7.89	$7.90	$7.90
Purchase #7	$140.31	5.222%	$147.637	$147.64	$147.65	$147.60
7 purchase totals =	$878.25		$925.8820	$925.90	$925.95	$925.80