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	$137.57	8.238%	$148.903	$148.90	$148.90	$148.90
Purchase #2	$120.40	9.338%	$131.643	$131.64	$131.65	$131.60
Purchase #3	$58.29	7.372%	$62.5871	$62.59	$62.60	$62.60
Purchase #4	$118.63	4.668%	$124.1676	$124.17	$124.15	$124.20
Purchase #5	$147.57	12.640%	$166.2228	$166.22	$166.20	$166.20
Purchase #6	$205.43	3.526%	$212.6735	$212.67	$212.65	$212.70
Purchase #7	$78.35	13.790%	$89.1545	$89.15	$89.15	$89.20
7 purchase totals =	$866.24		$935.3515	$935.34	$935.30	$935.40