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	$153.84	11.335%	$171.2778	$171.28	$171.30	$171.30
Purchase #2	$37.87	11.359%	$42.1717	$42.17	$42.15	$42.20
Purchase #3	$200.76	10.539%	$221.9181	$221.92	$221.90	$221.90
Purchase #4	$92.27	8.652%	$100.2532	$100.25	$100.25	$100.30
Purchase #5	$131.82	6.824%	$140.8154	$140.82	$140.80	$140.80
Purchase #6	$184.75	11.717%	$206.3972	$206.40	$206.40	$206.40
Purchase #7	$126.40	12.868%	$142.6652	$142.67	$142.65	$142.70
7 purchase totals =	$927.71		$1,025.4986	$1,025.51	$1,025.45	$1,025.60