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	$195.34	13.400%	$221.5156	$221.52	$221.50	$221.50
Purchase #2	$185.63	9.442%	$203.1572	$203.16	$203.15	$203.20
Purchase #3	$42.35	9.812%	$46.5054	$46.51	$46.50	$46.50
Purchase #4	$49.69	4.857%	$52.1034	$52.10	$52.10	$52.10
Purchase #5	$104.55	6.246%	$111.0802	$111.08	$111.10	$111.10
Purchase #6	$206.95	5.482%	$218.295	$218.30	$218.30	$218.30
Purchase #7	$167.38	11.208%	$186.14	$186.14	$186.15	$186.10
7 purchase totals =	$951.89		$1,038.7968	$1,038.81	$1,038.80	$1,038.80