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	$44.99	8.646%	$48.8798	$48.88	$48.90	$48.90
Purchase #2	$233.73	4.573%	$244.4185	$244.42	$244.40	$244.40
Purchase #3	$197.30	5.269%	$207.6957	$207.70	$207.70	$207.70
Purchase #4	$160.75	4.257%	$167.5931	$167.59	$167.60	$167.60
Purchase #5	$107.88	11.615%	$120.4103	$120.41	$120.40	$120.40
Purchase #6	$175.39	12.220%	$196.8227	$196.82	$196.80	$196.80
Purchase #7	$71.53	9.873%	$78.5922	$78.59	$78.60	$78.60
7 purchase totals =	$991.57		$1,064.4123	$1,064.41	$1,064.40	$1,064.40