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	$20.25	9.716%	$22.2175	$22.22	$22.20	$22.20
Purchase #2	$158.67	6.825%	$169.4992	$169.50	$169.50	$169.50
Purchase #3	$168.97	12.705%	$190.4376	$190.44	$190.45	$190.40
Purchase #4	$244.72	12.365%	$274.9796	$274.98	$275.00	$275.00
Purchase #5	$193.90	5.705%	$204.962	$204.96	$204.95	$205.00
Purchase #6	$74.75	4.840%	$78.3679	$78.37	$78.35	$78.40
Purchase #7	$99.46	9.647%	$109.0549	$109.05	$109.05	$109.10
7 purchase totals =	$960.72		$1,049.5187	$1,049.52	$1,049.50	$1,049.60