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	$207.91	3.440%	$215.0621	$215.06	$215.05	$215.10
Purchase #2	$129.56	12.862%	$146.224	$146.22	$146.20	$146.20
Purchase #3	$234.49	11.779%	$262.1106	$262.11	$262.10	$262.10
Purchase #4	$246.48	5.551%	$260.1621	$260.16	$260.15	$260.20
Purchase #5	$86.89	3.470%	$89.9051	$89.91	$89.90	$89.90
Purchase #6	$62.47	7.375%	$67.0772	$67.08	$67.10	$67.10
Purchase #7	$230.89	12.768%	$260.37	$260.37	$260.35	$260.40
7 purchase totals =	$1,198.69		$1,300.9111	$1,300.91	$1,300.85	$1,301.00