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	$208.76	9.389%	$228.3605	$228.36	$228.35	$228.40
Purchase #2	$62.29	6.541%	$66.3644	$66.36	$66.35	$66.40
Purchase #3	$123.83	12.556%	$139.3781	$139.38	$139.40	$139.40
Purchase #4	$160.77	7.374%	$172.6252	$172.63	$172.65	$172.60
Purchase #5	$173.90	12.190%	$195.0984	$195.10	$195.10	$195.10
Purchase #6	$188.66	6.179%	$200.3173	$200.32	$200.30	$200.30
Purchase #7	$95.41	4.746%	$99.9382	$99.94	$99.95	$99.90
7 purchase totals =	$1,013.62		$1,102.0821	$1,102.09	$1,102.10	$1,102.10