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	$250.59	4.437%	$261.7087	$261.71	$261.70	$261.70
Purchase #2	$212.95	7.430%	$228.7722	$228.77	$228.75	$228.80
Purchase #3	$147.57	5.828%	$156.1704	$156.17	$156.15	$156.20
Purchase #4	$99.41	8.264%	$107.6252	$107.63	$107.65	$107.60
Purchase #5	$44.36	9.376%	$48.5192	$48.52	$48.50	$48.50
Purchase #6	$189.87	3.691%	$196.8781	$196.88	$196.90	$196.90
Purchase #7	$100.90	10.712%	$111.7084	$111.71	$111.70	$111.70
7 purchase totals =	$1,045.65		$1,111.3822	$1,111.39	$1,111.35	$1,111.40