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	$116.27	13.794%	$132.3083	$132.31	$132.30	$132.30
Purchase #2	$20.27	5.868%	$21.4594	$21.46	$21.45	$21.50
Purchase #3	$89.60	9.170%	$97.8163	$97.82	$97.80	$97.80
Purchase #4	$219.61	12.334%	$246.6967	$246.70	$246.70	$246.70
Purchase #5	$53.95	10.570%	$59.6525	$59.65	$59.65	$59.70
Purchase #6	$53.91	6.391%	$57.3554	$57.36	$57.35	$57.40
Purchase #7	$49.92	11.821%	$55.821	$55.82	$55.80	$55.80
7 purchase totals =	$603.53		$671.1096	$671.12	$671.05	$671.20