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	$92.69	12.415%	$104.1975	$104.20	$104.20	$104.20
Purchase #2	$148.66	4.464%	$155.2962	$155.30	$155.30	$155.30
Purchase #3	$163.41	13.561%	$185.57	$185.57	$185.55	$185.60
Purchase #4	$248.69	13.641%	$282.6138	$282.61	$282.60	$282.60
Purchase #5	$169.82	11.336%	$189.0708	$189.07	$189.05	$189.10
Purchase #6	$116.72	3.151%	$120.3978	$120.40	$120.40	$120.40
Purchase #7	$62.67	7.564%	$67.4104	$67.41	$67.40	$67.40
7 purchase totals =	$1,002.66		$1,104.5565	$1,104.56	$1,104.50	$1,104.60