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	$56.78	4.844%	$59.5304	$59.53	$59.55	$59.50
Purchase #2	$248.90	6.290%	$264.5558	$264.56	$264.55	$264.60
Purchase #3	$45.90	11.472%	$51.1656	$51.17	$51.15	$51.20
Purchase #4	$22.90	11.725%	$25.585	$25.59	$25.60	$25.60
Purchase #5	$100.68	7.803%	$108.5361	$108.54	$108.55	$108.50
Purchase #6	$141.95	13.515%	$161.1345	$161.13	$161.15	$161.10
Purchase #7	$5.73	11.419%	$6.3843	$6.38	$6.40	$6.40
7 purchase totals =	$622.84		$676.8917	$676.90	$676.95	$676.90