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	$246.43	9.333%	$269.4293	$269.43	$269.45	$269.40
Purchase #2	$32.65	9.139%	$35.6339	$35.63	$35.65	$35.60
Purchase #3	$166.47	5.350%	$175.3761	$175.38	$175.40	$175.40
Purchase #4	$208.38	3.146%	$214.9356	$214.94	$214.95	$214.90
Purchase #5	$211.66	5.277%	$222.8293	$222.83	$222.85	$222.80
Purchase #6	$11.66	5.851%	$12.3422	$12.34	$12.35	$12.30
Purchase #7	$134.92	13.665%	$153.3568	$153.36	$153.35	$153.40
7 purchase totals =	$1,012.17		$1,083.9032	$1,083.91	$1,084.00	$1,083.80