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	$34.73	3.351%	$35.8938	$35.89	$35.90	$35.90
Purchase #2	$75.94	3.136%	$78.3215	$78.32	$78.30	$78.30
Purchase #3	$208.72	6.854%	$223.0257	$223.03	$223.05	$223.00
Purchase #4	$49.78	9.592%	$54.5549	$54.55	$54.55	$54.60
Purchase #5	$234.98	9.837%	$258.095	$258.10	$258.10	$258.10
Purchase #6	$127.69	7.570%	$137.3561	$137.36	$137.35	$137.40
Purchase #7	$84.73	3.787%	$87.9387	$87.94	$87.95	$87.90
7 purchase totals =	$816.57		$875.1857	$875.19	$875.20	$875.20