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	$211.30	4.797%	$221.4361	$221.44	$221.45	$221.40
Purchase #2	$38.37	13.229%	$43.446	$43.45	$43.45	$43.40
Purchase #3	$192.66	6.536%	$205.2523	$205.25	$205.25	$205.30
Purchase #4	$44.30	4.175%	$46.1495	$46.15	$46.15	$46.10
Purchase #5	$171.51	5.459%	$180.8727	$180.87	$180.85	$180.90
Purchase #6	$149.42	12.775%	$168.5084	$168.51	$168.50	$168.50
Purchase #7	$224.82	10.813%	$249.1298	$249.13	$249.15	$249.10
7 purchase totals =	$1,032.38		$1,114.7948	$1,114.80	$1,114.80	$1,114.70