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	$43.99	5.669%	$46.4838	$46.48	$46.50	$46.50
Purchase #2	$168.34	12.828%	$189.9347	$189.93	$189.95	$189.90
Purchase #3	$189.92	4.708%	$198.8614	$198.86	$198.85	$198.90
Purchase #4	$189.82	5.656%	$200.5562	$200.56	$200.55	$200.60
Purchase #5	$102.39	13.796%	$116.5157	$116.52	$116.50	$116.50
Purchase #6	$58.27	4.501%	$60.8927	$60.89	$60.90	$60.90
Purchase #7	$185.29	6.303%	$196.9688	$196.97	$196.95	$197.00
7 purchase totals =	$938.02		$1,010.2133	$1,010.21	$1,010.20	$1,010.30