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	$240.38	6.104%	$255.0528	$255.05	$255.05	$255.10
Purchase #2	$242.86	6.418%	$258.4468	$258.45	$258.45	$258.40
Purchase #3	$245.77	5.314%	$258.8302	$258.83	$258.85	$258.80
Purchase #4	$18.52	3.749%	$19.2143	$19.21	$19.20	$19.20
Purchase #5	$73.52	6.234%	$78.1032	$78.10	$78.10	$78.10
Purchase #6	$116.74	11.442%	$130.0974	$130.10	$130.10	$130.10
Purchase #7	$149.89	10.177%	$165.1443	$165.14	$165.15	$165.10
7 purchase totals =	$1,087.68		$1,164.8890	$1,164.88	$1,164.90	$1,164.80