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	$174.84	3.750%	$181.3965	$181.40	$181.40	$181.40
Purchase #2	$50.53	8.513%	$54.8316	$54.83	$54.85	$54.80
Purchase #3	$76.47	7.518%	$82.219	$82.22	$82.20	$82.20
Purchase #4	$216.89	12.783%	$244.615	$244.62	$244.60	$244.60
Purchase #5	$122.97	13.361%	$139.4	$139.40	$139.40	$139.40
Purchase #6	$188.66	13.754%	$214.6083	$214.61	$214.60	$214.60
Purchase #7	$250.80	12.260%	$281.5481	$281.55	$281.55	$281.50
7 purchase totals =	$1,081.16		$1,198.6185	$1,198.63	$1,198.60	$1,198.50