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	$187.78	7.164%	$201.2326	$201.23	$201.25	$201.20
Purchase #2	$179.50	4.396%	$187.3908	$187.39	$187.40	$187.40
Purchase #3	$36.77	3.240%	$37.9613	$37.96	$37.95	$38.00
Purchase #4	$120.54	11.422%	$134.3081	$134.31	$134.30	$134.30
Purchase #5	$173.86	6.678%	$185.4704	$185.47	$185.45	$185.50
Purchase #6	$197.28	12.486%	$221.9124	$221.91	$221.90	$221.90
Purchase #7	$43.82	10.808%	$48.5561	$48.56	$48.55	$48.60
7 purchase totals =	$939.55		$1,016.8317	$1,016.83	$1,016.80	$1,016.90