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	$103.58	10.245%	$114.1918	$114.19	$114.20	$114.20
Purchase #2	$123.47	6.105%	$131.0078	$131.01	$131.00	$131.00
Purchase #3	$48.40	8.148%	$52.3436	$52.34	$52.35	$52.30
Purchase #4	$79.55	12.225%	$89.275	$89.28	$89.30	$89.30
Purchase #5	$122.38	6.299%	$130.0887	$130.09	$130.10	$130.10
Purchase #6	$75.73	12.426%	$85.1402	$85.14	$85.15	$85.10
Purchase #7	$66.30	4.611%	$69.3571	$69.36	$69.35	$69.40
7 purchase totals =	$619.41		$671.4042	$671.41	$671.45	$671.40