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	$58.58	12.757%	$66.0531	$66.05	$66.05	$66.10
Purchase #2	$91.55	7.556%	$98.4675	$98.47	$98.45	$98.50
Purchase #3	$220.80	3.585%	$228.7157	$228.72	$228.70	$228.70
Purchase #4	$120.96	5.465%	$127.5705	$127.57	$127.55	$127.60
Purchase #5	$71.68	3.647%	$74.2942	$74.29	$74.30	$74.30
Purchase #6	$177.59	10.684%	$196.5637	$196.56	$196.55	$196.60
Purchase #7	$207.98	6.561%	$221.6256	$221.63	$221.65	$221.60
7 purchase totals =	$949.14		$1,013.2903	$1,013.29	$1,013.25	$1,013.40