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	$202.31	3.423%	$209.2351	$209.24	$209.25	$209.20
Purchase #2	$55.96	3.156%	$57.7261	$57.73	$57.75	$57.70
Purchase #3	$50.90	4.388%	$53.1335	$53.13	$53.15	$53.10
Purchase #4	$180.90	10.570%	$200.0211	$200.02	$200.00	$200.00
Purchase #5	$119.54	12.544%	$134.5351	$134.54	$134.55	$134.50
Purchase #6	$145.39	3.619%	$150.6517	$150.65	$150.65	$150.70
Purchase #7	$239.83	13.603%	$272.4541	$272.45	$272.45	$272.50
7 purchase totals =	$994.83		$1,077.7567	$1,077.76	$1,077.80	$1,077.70