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	$102.89	13.852%	$117.1423	$117.14	$117.15	$117.10
Purchase #2	$190.52	5.272%	$200.5642	$200.56	$200.55	$200.60
Purchase #3	$58.77	9.856%	$64.5624	$64.56	$64.55	$64.60
Purchase #4	$49.32	13.767%	$56.1099	$56.11	$56.10	$56.10
Purchase #5	$67.78	7.600%	$72.9313	$72.93	$72.95	$72.90
Purchase #6	$52.86	8.752%	$57.4863	$57.49	$57.50	$57.50
Purchase #7	$158.65	3.420%	$164.0758	$164.08	$164.10	$164.10
7 purchase totals =	$680.79		$732.8722	$732.87	$732.90	$732.90