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	$189.95	11.363%	$211.534	$211.53	$211.55	$211.50
Purchase #2	$224.88	13.855%	$256.0371	$256.04	$256.05	$256.00
Purchase #3	$99.76	10.177%	$109.9126	$109.91	$109.90	$109.90
Purchase #4	$197.35	6.338%	$209.858	$209.86	$209.85	$209.90
Purchase #5	$237.33	3.159%	$244.8273	$244.83	$244.85	$244.80
Purchase #6	$207.75	4.742%	$217.6015	$217.60	$217.60	$217.60
Purchase #7	$46.78	11.288%	$52.0605	$52.06	$52.05	$52.10
7 purchase totals =	$1,203.80		$1,301.8310	$1,301.83	$1,301.85	$1,301.80