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	$219.25	11.759%	$245.0316	$245.03	$245.05	$245.00
Purchase #2	$68.38	8.727%	$74.3475	$74.35	$74.35	$74.30
Purchase #3	$71.93	9.275%	$78.6015	$78.60	$78.60	$78.60
Purchase #4	$124.86	5.531%	$131.766	$131.77	$131.75	$131.80
Purchase #5	$187.95	5.238%	$197.7948	$197.79	$197.80	$197.80
Purchase #6	$142.94	9.354%	$156.3106	$156.31	$156.30	$156.30
Purchase #7	$42.34	7.223%	$45.3982	$45.40	$45.40	$45.40
7 purchase totals =	$857.65		$929.2502	$929.25	$929.25	$929.20