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	$55.84	10.147%	$61.5061	$61.51	$61.50	$61.50
Purchase #2	$159.35	7.736%	$171.6773	$171.68	$171.70	$171.70
Purchase #3	$78.54	13.603%	$89.2238	$89.22	$89.20	$89.20
Purchase #4	$189.40	6.269%	$201.2735	$201.27	$201.25	$201.30
Purchase #5	$20.76	4.537%	$21.7019	$21.70	$21.70	$21.70
Purchase #6	$170.95	6.853%	$182.6652	$182.67	$182.65	$182.70
Purchase #7	$144.81	13.860%	$164.8807	$164.88	$164.90	$164.90
7 purchase totals =	$819.65		$892.9285	$892.93	$892.90	$893.00