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	$65.44	7.445%	$70.312	$70.31	$70.30	$70.30
Purchase #2	$145.84	8.790%	$158.6593	$158.66	$158.65	$158.70
Purchase #3	$31.60	12.149%	$35.4391	$35.44	$35.45	$35.40
Purchase #4	$41.27	11.208%	$45.8955	$45.90	$45.90	$45.90
Purchase #5	$42.52	7.355%	$45.6473	$45.65	$45.65	$45.60
Purchase #6	$139.40	3.259%	$143.943	$143.94	$143.95	$143.90
Purchase #7	$57.66	11.467%	$64.2719	$64.27	$64.25	$64.30
7 purchase totals =	$523.73		$564.1681	$564.17	$564.15	$564.10