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	$41.43	5.661%	$43.7754	$43.78	$43.80	$43.80
Purchase #2	$7.97	7.163%	$8.5409	$8.54	$8.55	$8.50
Purchase #3	$66.51	6.324%	$70.7161	$70.72	$70.70	$70.70
Purchase #4	$179.26	4.259%	$186.8947	$186.89	$186.90	$186.90
Purchase #5	$35.76	7.397%	$38.4052	$38.41	$38.40	$38.40
Purchase #6	$188.47	8.439%	$204.375	$204.38	$204.40	$204.40
Purchase #7	$52.85	3.147%	$54.5132	$54.51	$54.50	$54.50
7 purchase totals =	$572.25		$607.2205	$607.23	$607.25	$607.20