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	$38.34	12.434%	$43.1072	$43.11	$43.10	$43.10
Purchase #2	$119.42	6.377%	$127.0354	$127.04	$127.05	$127.00
Purchase #3	$112.72	3.840%	$117.0484	$117.05	$117.05	$117.00
Purchase #4	$93.84	12.588%	$105.6526	$105.65	$105.65	$105.70
Purchase #5	$235.54	12.533%	$265.0602	$265.06	$265.05	$265.10
Purchase #6	$126.93	7.464%	$136.4041	$136.40	$136.40	$136.40
Purchase #7	$131.52	12.185%	$147.5457	$147.55	$147.55	$147.50
7 purchase totals =	$858.31		$941.8536	$941.86	$941.85	$941.80