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	$219.61	3.499%	$227.2942	$227.29	$227.30	$227.30
Purchase #2	$246.79	12.704%	$278.1422	$278.14	$278.15	$278.10
Purchase #3	$131.83	7.419%	$141.6105	$141.61	$141.60	$141.60
Purchase #4	$30.50	3.303%	$31.5074	$31.51	$31.50	$31.50
Purchase #5	$41.73	8.722%	$45.3697	$45.37	$45.35	$45.40
Purchase #6	$105.85	11.676%	$118.209	$118.21	$118.20	$118.20
Purchase #7	$128.61	10.121%	$141.6266	$141.63	$141.65	$141.60
7 purchase totals =	$904.92		$983.7596	$983.76	$983.75	$983.70