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	$116.89	7.529%	$125.6906	$125.69	$125.70	$125.70
Purchase #2	$113.61	9.277%	$124.1496	$124.15	$124.15	$124.10
Purchase #3	$54.67	11.538%	$60.9778	$60.98	$61.00	$61.00
Purchase #4	$179.54	9.513%	$196.6196	$196.62	$196.60	$196.60
Purchase #5	$241.64	5.320%	$254.4952	$254.50	$254.50	$254.50
Purchase #6	$50.55	9.309%	$55.2557	$55.26	$55.25	$55.30
Purchase #7	$82.94	7.848%	$89.4491	$89.45	$89.45	$89.40
7 purchase totals =	$839.84		$906.6376	$906.65	$906.65	$906.60