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	$197.93	12.265%	$222.2061	$222.21	$222.20	$222.20
Purchase #2	$218.82	4.768%	$229.2533	$229.25	$229.25	$229.30
Purchase #3	$169.82	11.619%	$189.5514	$189.55	$189.55	$189.60
Purchase #4	$103.59	9.524%	$113.4559	$113.46	$113.45	$113.50
Purchase #5	$52.29	3.550%	$54.1463	$54.15	$54.15	$54.10
Purchase #6	$52.72	12.304%	$59.2067	$59.21	$59.20	$59.20
Purchase #7	$137.47	7.423%	$147.6744	$147.67	$147.65	$147.70
7 purchase totals =	$932.64		$1,015.4941	$1,015.50	$1,015.45	$1,015.60