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	$51.83	7.280%	$55.6032	$55.60	$55.60	$55.60
Purchase #2	$228.57	11.127%	$254.003	$254.00	$254.00	$254.00
Purchase #3	$197.32	9.365%	$215.799	$215.80	$215.80	$215.80
Purchase #4	$108.98	3.600%	$112.9033	$112.90	$112.90	$112.90
Purchase #5	$51.53	9.388%	$56.3676	$56.37	$56.35	$56.40
Purchase #6	$209.31	11.128%	$232.602	$232.60	$232.60	$232.60
Purchase #7	$209.32	10.403%	$231.0956	$231.10	$231.10	$231.10
7 purchase totals =	$1,056.86		$1,158.3737	$1,158.37	$1,158.35	$1,158.40