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	$107.71	10.795%	$119.3373	$119.34	$119.35	$119.30
Purchase #2	$60.62	7.581%	$65.2156	$65.22	$65.20	$65.20
Purchase #3	$35.83	11.291%	$39.8756	$39.88	$39.90	$39.90
Purchase #4	$114.47	11.688%	$127.8493	$127.85	$127.85	$127.80
Purchase #5	$239.37	8.562%	$259.8649	$259.86	$259.85	$259.90
Purchase #6	$200.29	5.282%	$210.8693	$210.87	$210.85	$210.90
Purchase #7	$180.94	4.457%	$189.0045	$189.00	$189.00	$189.00
7 purchase totals =	$939.23		$1,012.0165	$1,012.02	$1,012.00	$1,012.00