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	$236.51	11.751%	$264.3023	$264.30	$264.30	$264.30
Purchase #2	$176.92	3.377%	$182.8946	$182.89	$182.90	$182.90
Purchase #3	$72.82	3.727%	$75.534	$75.53	$75.55	$75.50
Purchase #4	$112.28	11.841%	$125.5751	$125.58	$125.60	$125.60
Purchase #5	$64.48	11.802%	$72.0899	$72.09	$72.10	$72.10
Purchase #6	$119.88	6.197%	$127.309	$127.31	$127.30	$127.30
Purchase #7	$246.29	10.521%	$272.2022	$272.20	$272.20	$272.20
7 purchase totals =	$1,029.18		$1,119.9071	$1,119.90	$1,119.95	$1,119.90