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	$176.42	3.719%	$182.9811	$182.98	$183.00	$183.00
Purchase #2	$41.95	13.475%	$47.6028	$47.60	$47.60	$47.60
Purchase #3	$115.34	13.645%	$131.0781	$131.08	$131.10	$131.10
Purchase #4	$46.40	6.357%	$49.3496	$49.35	$49.35	$49.30
Purchase #5	$53.80	12.740%	$60.6541	$60.65	$60.65	$60.70
Purchase #6	$42.29	7.818%	$45.5962	$45.60	$45.60	$45.60
Purchase #7	$14.28	5.343%	$15.043	$15.04	$15.05	$15.00
7 purchase totals =	$490.48		$532.3049	$532.30	$532.35	$532.30