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	$200.75	11.705%	$224.2478	$224.25	$224.25	$224.20
Purchase #2	$81.72	9.647%	$89.6035	$89.60	$89.60	$89.60
Purchase #3	$189.60	3.168%	$195.6065	$195.61	$195.60	$195.60
Purchase #4	$145.72	5.802%	$154.1747	$154.17	$154.15	$154.20
Purchase #5	$110.27	5.824%	$116.6921	$116.69	$116.70	$116.70
Purchase #6	$141.47	11.308%	$157.4674	$157.47	$157.45	$157.50
Purchase #7	$214.30	13.683%	$243.6227	$243.62	$243.60	$243.60
7 purchase totals =	$1,083.83		$1,181.4147	$1,181.41	$1,181.35	$1,181.40