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	$43.91	11.498%	$48.9588	$48.96	$48.95	$49.00
Purchase #2	$176.66	11.229%	$196.4972	$196.50	$196.50	$196.50
Purchase #3	$20.82	4.149%	$21.6838	$21.68	$21.70	$21.70
Purchase #4	$111.68	6.690%	$119.1514	$119.15	$119.15	$119.20
Purchase #5	$39.91	9.865%	$43.8471	$43.85	$43.85	$43.80
Purchase #6	$167.57	6.822%	$179.0016	$179.00	$179.00	$179.00
Purchase #7	$206.99	4.396%	$216.0893	$216.09	$216.10	$216.10
7 purchase totals =	$767.54		$825.2292	$825.23	$825.25	$825.30