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	$88.84	13.617%	$100.9373	$100.94	$100.95	$100.90
Purchase #2	$185.25	7.142%	$198.4806	$198.48	$198.50	$198.50
Purchase #3	$63.58	13.779%	$72.3407	$72.34	$72.35	$72.30
Purchase #4	$197.51	13.262%	$223.7038	$223.70	$223.70	$223.70
Purchase #5	$109.34	10.294%	$120.5955	$120.60	$120.60	$120.60
Purchase #6	$118.71	6.565%	$126.5033	$126.50	$126.50	$126.50
Purchase #7	$187.30	11.694%	$209.2029	$209.20	$209.20	$209.20
7 purchase totals =	$950.53		$1,051.7641	$1,051.76	$1,051.80	$1,051.70