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	$201.25	13.828%	$229.0789	$229.08	$229.10	$229.10
Purchase #2	$198.96	5.744%	$210.3883	$210.39	$210.40	$210.40
Purchase #3	$179.56	3.512%	$185.8661	$185.87	$185.85	$185.90
Purchase #4	$240.49	10.319%	$265.3062	$265.31	$265.30	$265.30
Purchase #5	$164.47	13.874%	$187.2886	$187.29	$187.30	$187.30
Purchase #6	$227.45	11.299%	$253.1496	$253.15	$253.15	$253.10
Purchase #7	$71.59	10.203%	$78.8943	$78.89	$78.90	$78.90
7 purchase totals =	$1,283.77		$1,409.9720	$1,409.98	$1,410.00	$1,410.00