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	$166.87	4.789%	$174.8614	$174.86	$174.85	$174.90
Purchase #2	$243.51	9.871%	$267.5469	$267.55	$267.55	$267.50
Purchase #3	$139.28	12.559%	$156.7722	$156.77	$156.75	$156.80
Purchase #4	$178.59	9.751%	$196.0043	$196.00	$196.00	$196.00
Purchase #5	$241.51	12.574%	$271.8775	$271.88	$271.90	$271.90
Purchase #6	$88.70	10.538%	$98.0472	$98.05	$98.05	$98.00
Purchase #7	$101.65	4.772%	$106.5007	$106.50	$106.50	$106.50
7 purchase totals =	$1,160.11		$1,271.6102	$1,271.61	$1,271.60	$1,271.60