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	$222.59	3.708%	$230.8436	$230.84	$230.85	$230.80
Purchase #2	$165.73	8.199%	$179.3182	$179.32	$179.30	$179.30
Purchase #3	$72.34	8.381%	$78.4028	$78.40	$78.40	$78.40
Purchase #4	$32.80	9.513%	$35.9203	$35.92	$35.90	$35.90
Purchase #5	$237.86	11.569%	$265.378	$265.38	$265.40	$265.40
Purchase #6	$102.39	13.321%	$116.0294	$116.03	$116.05	$116.00
Purchase #7	$247.50	10.236%	$272.8341	$272.83	$272.85	$272.80
7 purchase totals =	$1,081.21		$1,178.7264	$1,178.72	$1,178.75	$1,178.60