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	$137.29	3.610%	$142.2462	$142.25	$142.25	$142.20
Purchase #2	$179.37	11.671%	$200.3043	$200.30	$200.30	$200.30
Purchase #3	$49.79	11.774%	$55.6523	$55.65	$55.65	$55.70
Purchase #4	$233.83	12.449%	$262.9395	$262.94	$262.95	$262.90
Purchase #5	$120.34	6.485%	$128.144	$128.14	$128.15	$128.10
Purchase #6	$46.67	9.385%	$51.05	$51.05	$51.05	$51.10
Purchase #7	$166.27	12.185%	$186.53	$186.53	$186.55	$186.50
7 purchase totals =	$933.56		$1,026.8663	$1,026.86	$1,026.90	$1,026.80