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	$49.34	8.518%	$53.5428	$53.54	$53.55	$53.50
Purchase #2	$188.40	5.341%	$198.4624	$198.46	$198.45	$198.50
Purchase #3	$192.74	6.784%	$205.8155	$205.82	$205.80	$205.80
Purchase #4	$192.28	13.311%	$217.8744	$217.87	$217.85	$217.90
Purchase #5	$150.47	11.651%	$168.0013	$168.00	$168.00	$168.00
Purchase #6	$87.38	3.369%	$90.3238	$90.32	$90.30	$90.30
Purchase #7	$172.63	12.690%	$194.5367	$194.54	$194.55	$194.50
7 purchase totals =	$1,033.24		$1,128.5569	$1,128.55	$1,128.50	$1,128.50