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	$37.44	10.590%	$41.4049	$41.40	$41.40	$41.40
Purchase #2	$27.89	12.372%	$31.3406	$31.34	$31.35	$31.30
Purchase #3	$52.55	13.447%	$59.6164	$59.62	$59.60	$59.60
Purchase #4	$60.89	6.778%	$65.0171	$65.02	$65.00	$65.00
Purchase #5	$71.83	9.458%	$78.6237	$78.62	$78.60	$78.60
Purchase #6	$79.95	3.676%	$82.889	$82.89	$82.90	$82.90
Purchase #7	$45.91	13.430%	$52.0757	$52.08	$52.10	$52.10
7 purchase totals =	$376.46		$410.9674	$410.97	$410.95	$410.90