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	$99.89	12.724%	$112.6	$112.60	$112.60	$112.60
Purchase #2	$164.72	7.242%	$176.649	$176.65	$176.65	$176.60
Purchase #3	$12.32	11.577%	$13.7463	$13.75	$13.75	$13.70
Purchase #4	$111.85	3.565%	$115.8375	$115.84	$115.85	$115.80
Purchase #5	$212.75	10.168%	$234.3824	$234.38	$234.40	$234.40
Purchase #6	$171.77	7.792%	$185.1543	$185.15	$185.15	$185.20
Purchase #7	$98.53	7.454%	$105.8744	$105.87	$105.85	$105.90
7 purchase totals =	$871.83		$944.2439	$944.24	$944.25	$944.20