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	$80.61	9.306%	$88.1116	$88.11	$88.10	$88.10
Purchase #2	$174.87	10.678%	$193.5426	$193.54	$193.55	$193.50
Purchase #3	$104.71	4.294%	$109.2062	$109.21	$109.20	$109.20
Purchase #4	$194.39	5.685%	$205.4411	$205.44	$205.45	$205.40
Purchase #5	$103.83	5.661%	$109.7078	$109.71	$109.70	$109.70
Purchase #6	$145.56	6.687%	$155.2936	$155.29	$155.30	$155.30
Purchase #7	$211.77	4.471%	$221.2382	$221.24	$221.25	$221.20
7 purchase totals =	$1,015.74		$1,082.5411	$1,082.54	$1,082.55	$1,082.40