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	$187.51	9.500%	$205.3235	$205.32	$205.30	$205.30
Purchase #2	$144.69	12.550%	$162.8486	$162.85	$162.85	$162.80
Purchase #3	$114.37	3.439%	$118.3032	$118.30	$118.30	$118.30
Purchase #4	$51.41	12.337%	$57.7525	$57.75	$57.75	$57.80
Purchase #5	$87.98	7.870%	$94.904	$94.90	$94.90	$94.90
Purchase #6	$7.70	3.111%	$7.9395	$7.94	$7.95	$7.90
Purchase #7	$30.89	13.661%	$35.1099	$35.11	$35.10	$35.10
7 purchase totals =	$624.55		$682.1812	$682.17	$682.15	$682.10