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	$241.33	7.277%	$258.8916	$258.89	$258.90	$258.90
Purchase #2	$85.65	9.832%	$94.0711	$94.07	$94.05	$94.10
Purchase #3	$116.43	9.638%	$127.6515	$127.65	$127.65	$127.70
Purchase #4	$86.99	3.544%	$90.0729	$90.07	$90.05	$90.10
Purchase #5	$119.84	4.727%	$125.5048	$125.50	$125.50	$125.50
Purchase #6	$187.55	5.481%	$197.8296	$197.83	$197.85	$197.80
Purchase #7	$35.62	4.740%	$37.3084	$37.31	$37.30	$37.30
7 purchase totals =	$873.41		$931.3299	$931.32	$931.30	$931.40