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	$141.49	3.116%	$145.8988	$145.90	$145.90	$145.90
Purchase #2	$162.37	3.533%	$168.1065	$168.11	$168.10	$168.10
Purchase #3	$22.25	10.187%	$24.5166	$24.52	$24.50	$24.50
Purchase #4	$205.38	9.648%	$225.1951	$225.20	$225.20	$225.20
Purchase #5	$192.95	10.340%	$212.901	$212.90	$212.90	$212.90
Purchase #6	$53.96	3.422%	$55.8065	$55.81	$55.80	$55.80
Purchase #7	$221.28	12.479%	$248.8935	$248.89	$248.90	$248.90
7 purchase totals =	$999.68		$1,081.3180	$1,081.33	$1,081.30	$1,081.30