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	$149.76	9.861%	$164.5278	$164.53	$164.55	$164.50
Purchase #2	$16.48	13.759%	$18.7475	$18.75	$18.75	$18.70
Purchase #3	$53.46	8.312%	$57.9036	$57.90	$57.90	$57.90
Purchase #4	$128.74	6.713%	$137.3823	$137.38	$137.40	$137.40
Purchase #5	$135.87	4.554%	$142.0575	$142.06	$142.05	$142.10
Purchase #6	$140.82	4.598%	$147.2949	$147.29	$147.30	$147.30
Purchase #7	$94.33	12.296%	$105.9288	$105.93	$105.95	$105.90
7 purchase totals =	$719.46		$773.8424	$773.84	$773.90	$773.80