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	$159.40	6.576%	$169.8821	$169.88	$169.90	$169.90
Purchase #2	$46.41	8.351%	$50.2857	$50.29	$50.30	$50.30
Purchase #3	$84.70	7.279%	$90.8653	$90.87	$90.85	$90.90
Purchase #4	$12.77	9.740%	$14.0138	$14.01	$14.00	$14.00
Purchase #5	$199.86	9.838%	$219.5222	$219.52	$219.50	$219.50
Purchase #6	$105.64	6.156%	$112.1432	$112.14	$112.15	$112.10
Purchase #7	$245.57	6.700%	$262.0232	$262.02	$262.00	$262.00
7 purchase totals =	$854.35		$918.7355	$918.73	$918.70	$918.70