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	$233.29	6.499%	$248.4515	$248.45	$248.45	$248.50
Purchase #2	$59.91	6.233%	$63.6442	$63.64	$63.65	$63.60
Purchase #3	$50.84	8.186%	$55.0018	$55.00	$55.00	$55.00
Purchase #4	$192.68	10.338%	$212.5993	$212.60	$212.60	$212.60
Purchase #5	$141.54	6.344%	$150.5193	$150.52	$150.50	$150.50
Purchase #6	$174.45	6.290%	$185.4229	$185.42	$185.40	$185.40
Purchase #7	$203.87	11.148%	$226.5974	$226.60	$226.60	$226.60
7 purchase totals =	$1,056.58		$1,142.2364	$1,142.23	$1,142.20	$1,142.20