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	$94.94	5.354%	$100.0231	$100.02	$100.00	$100.00
Purchase #2	$106.57	3.165%	$109.9429	$109.94	$109.95	$109.90
Purchase #3	$95.65	12.242%	$107.3595	$107.36	$107.35	$107.40
Purchase #4	$126.26	13.355%	$143.122	$143.12	$143.10	$143.10
Purchase #5	$28.71	11.732%	$32.0783	$32.08	$32.10	$32.10
Purchase #6	$35.53	12.479%	$39.9638	$39.96	$39.95	$40.00
Purchase #7	$83.41	7.383%	$89.5682	$89.57	$89.55	$89.60
7 purchase totals =	$571.07		$622.0578	$622.05	$622.00	$622.10