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	$92.35	10.355%	$101.9128	$101.91	$101.90	$101.90
Purchase #2	$93.91	5.820%	$99.3756	$99.38	$99.40	$99.40
Purchase #3	$57.66	12.789%	$65.0341	$65.03	$65.05	$65.00
Purchase #4	$159.78	11.445%	$178.0668	$178.07	$178.05	$178.10
Purchase #5	$186.58	5.630%	$197.0845	$197.08	$197.10	$197.10
Purchase #6	$232.66	12.532%	$261.817	$261.82	$261.80	$261.80
Purchase #7	$185.93	7.856%	$200.5367	$200.54	$200.55	$200.50
7 purchase totals =	$1,008.87		$1,103.8275	$1,103.83	$1,103.85	$1,103.80