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	$157.33	5.152%	$165.4356	$165.44	$165.45	$165.40
Purchase #2	$141.59	7.408%	$152.079	$152.08	$152.10	$152.10
Purchase #3	$17.91	8.400%	$19.4144	$19.41	$19.40	$19.40
Purchase #4	$124.92	6.123%	$132.5689	$132.57	$132.55	$132.60
Purchase #5	$164.89	7.309%	$176.9418	$176.94	$176.95	$176.90
Purchase #6	$55.40	10.283%	$61.0968	$61.10	$61.10	$61.10
Purchase #7	$111.27	4.705%	$116.5053	$116.51	$116.50	$116.50
7 purchase totals =	$773.31		$824.0418	$824.05	$824.05	$824.00