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	$43.41	11.483%	$48.3948	$48.39	$48.40	$48.40
Purchase #2	$151.99	11.306%	$169.174	$169.17	$169.15	$169.20
Purchase #3	$85.30	13.371%	$96.7055	$96.71	$96.70	$96.70
Purchase #4	$98.70	12.611%	$111.1471	$111.15	$111.15	$111.10
Purchase #5	$109.46	4.716%	$114.6221	$114.62	$114.60	$114.60
Purchase #6	$195.49	10.264%	$215.5551	$215.56	$215.55	$215.60
Purchase #7	$219.37	3.536%	$227.1269	$227.13	$227.15	$227.10
7 purchase totals =	$903.72		$982.7255	$982.73	$982.70	$982.70