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	$237.56	13.168%	$268.8419	$268.84	$268.85	$268.80
Purchase #2	$31.58	3.753%	$32.7652	$32.77	$32.75	$32.80
Purchase #3	$116.68	3.216%	$120.4324	$120.43	$120.45	$120.40
Purchase #4	$126.27	6.836%	$134.9018	$134.90	$134.90	$134.90
Purchase #5	$118.55	4.177%	$123.5018	$123.50	$123.50	$123.50
Purchase #6	$114.63	7.354%	$123.0599	$123.06	$123.05	$123.10
Purchase #7	$130.49	11.739%	$145.8082	$145.81	$145.80	$145.80
7 purchase totals =	$875.76		$949.3112	$949.31	$949.30	$949.30