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	$9.49	13.506%	$10.7717	$10.77	$10.75	$10.80
Purchase #2	$35.62	4.795%	$37.328	$37.33	$37.35	$37.30
Purchase #3	$102.62	6.737%	$109.5335	$109.53	$109.55	$109.50
Purchase #4	$57.58	8.651%	$62.5612	$62.56	$62.55	$62.60
Purchase #5	$223.84	6.250%	$237.83	$237.83	$237.85	$237.80
Purchase #6	$181.82	9.726%	$199.5038	$199.50	$199.50	$199.50
Purchase #7	$155.31	13.192%	$175.7985	$175.80	$175.80	$175.80
7 purchase totals =	$766.28		$833.3267	$833.32	$833.35	$833.30