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	$85.64	7.419%	$91.9936	$91.99	$92.00	$92.00
Purchase #2	$41.40	5.329%	$43.6062	$43.61	$43.60	$43.60
Purchase #3	$176.70	11.459%	$196.9481	$196.95	$196.95	$196.90
Purchase #4	$113.98	3.617%	$118.1027	$118.10	$118.10	$118.10
Purchase #5	$42.73	5.841%	$45.2259	$45.23	$45.25	$45.20
Purchase #6	$107.31	13.380%	$121.6681	$121.67	$121.65	$121.70
Purchase #7	$96.40	10.139%	$106.174	$106.17	$106.15	$106.20
7 purchase totals =	$664.16		$723.7186	$723.72	$723.70	$723.70