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	$147.77	11.367%	$164.567	$164.57	$164.55	$164.60
Purchase #2	$20.30	5.588%	$21.4344	$21.43	$21.45	$21.40
Purchase #3	$215.67	4.614%	$225.621	$225.62	$225.60	$225.60
Purchase #4	$150.59	6.228%	$159.9687	$159.97	$159.95	$160.00
Purchase #5	$199.32	7.146%	$213.5634	$213.56	$213.55	$213.60
Purchase #6	$126.56	5.584%	$133.6271	$133.63	$133.65	$133.60
Purchase #7	$74.44	5.395%	$78.456	$78.46	$78.45	$78.50
7 purchase totals =	$934.65		$997.2376	$997.24	$997.20	$997.30