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	$75.93	8.825%	$82.6308	$82.63	$82.65	$82.60
Purchase #2	$218.42	9.219%	$238.5561	$238.56	$238.55	$238.60
Purchase #3	$179.43	13.396%	$203.4664	$203.47	$203.45	$203.50
Purchase #4	$222.95	8.229%	$241.2966	$241.30	$241.30	$241.30
Purchase #5	$125.32	12.746%	$141.2933	$141.29	$141.30	$141.30
Purchase #6	$99.73	9.511%	$109.2153	$109.22	$109.20	$109.20
Purchase #7	$45.76	8.325%	$49.5695	$49.57	$49.55	$49.60
7 purchase totals =	$967.54		$1,066.0280	$1,066.04	$1,066.00	$1,066.10