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	$175.93	6.311%	$187.0329	$187.03	$187.05	$187.00
Purchase #2	$175.90	7.621%	$189.3053	$189.31	$189.30	$189.30
Purchase #3	$72.71	7.312%	$78.0266	$78.03	$78.05	$78.00
Purchase #4	$98.91	4.864%	$103.721	$103.72	$103.70	$103.70
Purchase #5	$162.31	3.503%	$167.9957	$168.00	$168.00	$168.00
Purchase #6	$7.89	13.369%	$8.9448	$8.94	$8.95	$8.90
Purchase #7	$190.47	11.515%	$212.4026	$212.40	$212.40	$212.40
7 purchase totals =	$884.12		$947.4289	$947.43	$947.45	$947.30