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	$178.58	9.323%	$195.229	$195.23	$195.25	$195.20
Purchase #2	$72.89	9.861%	$80.0777	$80.08	$80.10	$80.10
Purchase #3	$72.79	7.593%	$78.3169	$78.32	$78.30	$78.30
Purchase #4	$19.51	4.239%	$20.337	$20.34	$20.35	$20.30
Purchase #5	$41.27	4.102%	$42.9629	$42.96	$42.95	$43.00
Purchase #6	$46.52	8.546%	$50.4956	$50.50	$50.50	$50.50
Purchase #7	$84.62	5.685%	$89.4306	$89.43	$89.45	$89.40
7 purchase totals =	$516.18		$556.8497	$556.86	$556.90	$556.80