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	$84.72	7.221%	$90.8376	$90.84	$90.85	$90.80
Purchase #2	$157.43	3.473%	$162.8975	$162.90	$162.90	$162.90
Purchase #3	$104.66	3.511%	$108.3346	$108.33	$108.35	$108.30
Purchase #4	$35.92	8.112%	$38.8338	$38.83	$38.85	$38.80
Purchase #5	$196.39	9.426%	$214.9017	$214.90	$214.90	$214.90
Purchase #6	$8.31	13.789%	$9.4559	$9.46	$9.45	$9.50
Purchase #7	$88.60	11.735%	$98.9972	$99.00	$99.00	$99.00
7 purchase totals =	$676.03		$724.2583	$724.26	$724.30	$724.20