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	$52.31	13.532%	$59.3886	$59.39	$59.40	$59.40
Purchase #2	$27.76	4.197%	$28.9251	$28.93	$28.95	$28.90
Purchase #3	$214.36	4.465%	$223.9312	$223.93	$223.95	$223.90
Purchase #4	$166.35	3.320%	$171.8728	$171.87	$171.85	$171.90
Purchase #5	$143.34	8.424%	$155.415	$155.42	$155.40	$155.40
Purchase #6	$220.55	8.363%	$238.9946	$238.99	$239.00	$239.00
Purchase #7	$243.60	13.535%	$276.5713	$276.57	$276.55	$276.60
7 purchase totals =	$1,068.27		$1,155.0986	$1,155.10	$1,155.10	$1,155.10