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	$99.86	4.549%	$104.4026	$104.40	$104.40	$104.40
Purchase #2	$174.77	5.814%	$184.9311	$184.93	$184.95	$184.90
Purchase #3	$157.58	8.639%	$171.1933	$171.19	$171.20	$171.20
Purchase #4	$111.54	4.202%	$116.2269	$116.23	$116.25	$116.20
Purchase #5	$157.89	6.127%	$167.5639	$167.56	$167.55	$167.60
Purchase #6	$205.86	12.160%	$230.8926	$230.89	$230.90	$230.90
Purchase #7	$141.95	10.259%	$156.5127	$156.51	$156.50	$156.50
7 purchase totals =	$1,049.45		$1,131.7231	$1,131.71	$1,131.75	$1,131.70