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	$168.33	8.406%	$182.4798	$182.48	$182.50	$182.50
Purchase #2	$216.40	11.681%	$241.6777	$241.68	$241.70	$241.70
Purchase #3	$157.89	4.300%	$164.6793	$164.68	$164.70	$164.70
Purchase #4	$109.71	9.687%	$120.3376	$120.34	$120.35	$120.30
Purchase #5	$151.56	12.112%	$169.9169	$169.92	$169.90	$169.90
Purchase #6	$106.32	11.850%	$118.9189	$118.92	$118.90	$118.90
Purchase #7	$172.56	4.829%	$180.8929	$180.89	$180.90	$180.90
7 purchase totals =	$1,082.77		$1,178.9031	$1,178.91	$1,178.95	$1,178.90