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	$230.71	8.764%	$250.9294	$250.93	$250.95	$250.90
Purchase #2	$228.60	4.849%	$239.6848	$239.68	$239.70	$239.70
Purchase #3	$39.88	6.522%	$42.481	$42.48	$42.50	$42.50
Purchase #4	$84.49	9.409%	$92.4397	$92.44	$92.45	$92.40
Purchase #5	$156.82	10.245%	$172.8862	$172.89	$172.90	$172.90
Purchase #6	$109.46	9.165%	$119.492	$119.49	$119.50	$119.50
Purchase #7	$169.47	9.349%	$185.3138	$185.31	$185.30	$185.30
7 purchase totals =	$1,019.43		$1,103.2269	$1,103.22	$1,103.30	$1,103.20