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	$164.60	6.137%	$174.7015	$174.70	$174.70	$174.70
Purchase #2	$42.72	10.523%	$47.2154	$47.22	$47.20	$47.20
Purchase #3	$224.49	3.306%	$231.9116	$231.91	$231.90	$231.90
Purchase #4	$205.25	11.621%	$229.1021	$229.10	$229.10	$229.10
Purchase #5	$174.93	12.253%	$196.3642	$196.36	$196.35	$196.40
Purchase #6	$13.43	5.200%	$14.1284	$14.13	$14.15	$14.10
Purchase #7	$179.40	4.123%	$186.7967	$186.80	$186.80	$186.80
7 purchase totals =	$1,004.82		$1,080.2199	$1,080.22	$1,080.20	$1,080.20