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	$109.57	10.150%	$120.6914	$120.69	$120.70	$120.70
Purchase #2	$178.49	6.409%	$189.9294	$189.93	$189.95	$189.90
Purchase #3	$180.31	13.437%	$204.5383	$204.54	$204.55	$204.50
Purchase #4	$93.50	10.623%	$103.4325	$103.43	$103.45	$103.40
Purchase #5	$222.50	11.589%	$248.2855	$248.29	$248.30	$248.30
Purchase #6	$146.83	4.627%	$153.6238	$153.62	$153.60	$153.60
Purchase #7	$87.70	5.423%	$92.456	$92.46	$92.45	$92.50
7 purchase totals =	$1,018.90		$1,112.9569	$1,112.96	$1,113.00	$1,112.90