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	$9.54	10.458%	$10.5377	$10.54	$10.55	$10.50
Purchase #2	$71.96	5.779%	$76.1186	$76.12	$76.10	$76.10
Purchase #3	$236.54	11.139%	$262.8882	$262.89	$262.90	$262.90
Purchase #4	$219.45	11.834%	$245.4197	$245.42	$245.40	$245.40
Purchase #5	$36.67	5.573%	$38.7136	$38.71	$38.70	$38.70
Purchase #6	$49.88	5.435%	$52.591	$52.59	$52.60	$52.60
Purchase #7	$69.94	13.682%	$79.5092	$79.51	$79.50	$79.50
7 purchase totals =	$693.98		$765.7780	$765.78	$765.75	$765.70