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	$196.95	12.332%	$221.2379	$221.24	$221.25	$221.20
Purchase #2	$47.59	11.404%	$53.0172	$53.02	$53.00	$53.00
Purchase #3	$245.96	5.602%	$259.7387	$259.74	$259.75	$259.70
Purchase #4	$35.29	13.393%	$40.0164	$40.02	$40.00	$40.00
Purchase #5	$109.62	12.631%	$123.4661	$123.47	$123.45	$123.50
Purchase #6	$59.62	9.696%	$65.4008	$65.40	$65.40	$65.40
Purchase #7	$171.83	5.721%	$181.6604	$181.66	$181.65	$181.70
7 purchase totals =	$866.86		$944.5375	$944.55	$944.50	$944.50