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	$185.99	7.206%	$199.3924	$199.39	$199.40	$199.40
Purchase #2	$178.78	3.513%	$185.0605	$185.06	$185.05	$185.10
Purchase #3	$43.53	4.284%	$45.3948	$45.39	$45.40	$45.40
Purchase #4	$235.86	13.483%	$267.661	$267.66	$267.65	$267.70
Purchase #5	$196.25	7.376%	$210.7254	$210.73	$210.75	$210.70
Purchase #6	$113.25	11.450%	$126.2171	$126.22	$126.20	$126.20
Purchase #7	$137.93	12.414%	$155.0526	$155.05	$155.05	$155.10
7 purchase totals =	$1,091.59		$1,189.5038	$1,189.50	$1,189.50	$1,189.60