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	$53.83	5.147%	$56.6006	$56.60	$56.60	$56.60
Purchase #2	$57.79	11.619%	$64.5046	$64.50	$64.50	$64.50
Purchase #3	$171.92	9.631%	$188.4776	$188.48	$188.50	$188.50
Purchase #4	$167.46	10.733%	$185.4335	$185.43	$185.45	$185.40
Purchase #5	$248.35	6.798%	$265.2328	$265.23	$265.25	$265.20
Purchase #6	$135.46	5.375%	$142.741	$142.74	$142.75	$142.70
Purchase #7	$226.80	10.736%	$251.1492	$251.15	$251.15	$251.10
7 purchase totals =	$1,061.61		$1,154.1393	$1,154.13	$1,154.20	$1,154.00