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	$67.35	13.593%	$76.5049	$76.50	$76.50	$76.50
Purchase #2	$37.25	6.160%	$39.5446	$39.54	$39.55	$39.50
Purchase #3	$78.84	5.789%	$83.404	$83.40	$83.40	$83.40
Purchase #4	$147.94	13.529%	$167.9548	$167.95	$167.95	$168.00
Purchase #5	$58.69	9.842%	$64.4663	$64.47	$64.45	$64.50
Purchase #6	$230.57	4.280%	$240.4384	$240.44	$240.45	$240.40
Purchase #7	$134.46	10.827%	$149.018	$149.02	$149.00	$149.00
7 purchase totals =	$755.10		$821.3310	$821.32	$821.30	$821.30