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	$89.74	7.440%	$96.4167	$96.42	$96.40	$96.40
Purchase #2	$38.40	5.853%	$40.6476	$40.65	$40.65	$40.60
Purchase #3	$186.61	13.285%	$211.4011	$211.40	$211.40	$211.40
Purchase #4	$214.90	13.799%	$244.5541	$244.55	$244.55	$244.60
Purchase #5	$175.31	7.487%	$188.4355	$188.44	$188.45	$188.40
Purchase #6	$197.92	8.612%	$214.9649	$214.96	$214.95	$215.00
Purchase #7	$36.94	8.322%	$40.0141	$40.01	$40.00	$40.00
7 purchase totals =	$939.82		$1,036.4340	$1,036.43	$1,036.40	$1,036.40