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	$119.26	9.808%	$130.957	$130.96	$130.95	$131.00
Purchase #2	$55.41	7.720%	$59.6877	$59.69	$59.70	$59.70
Purchase #3	$72.26	11.320%	$80.4398	$80.44	$80.45	$80.40
Purchase #4	$104.33	6.558%	$111.172	$111.17	$111.15	$111.20
Purchase #5	$27.46	8.357%	$29.7548	$29.75	$29.75	$29.80
Purchase #6	$24.67	11.531%	$27.5147	$27.51	$27.50	$27.50
Purchase #7	$26.47	5.723%	$27.9849	$27.98	$28.00	$28.00
7 purchase totals =	$429.86		$467.5109	$467.50	$467.50	$467.60