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	$164.61	10.573%	$182.0142	$182.01	$182.00	$182.00
Purchase #2	$180.63	11.866%	$202.0636	$202.06	$202.05	$202.10
Purchase #3	$86.87	3.170%	$89.6238	$89.62	$89.60	$89.60
Purchase #4	$96.67	13.727%	$109.9399	$109.94	$109.95	$109.90
Purchase #5	$104.68	4.733%	$109.6345	$109.63	$109.65	$109.60
Purchase #6	$31.41	7.667%	$33.8182	$33.82	$33.80	$33.80
Purchase #7	$47.88	3.134%	$49.3806	$49.38	$49.40	$49.40
7 purchase totals =	$712.75		$776.4748	$776.46	$776.45	$776.40