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	$163.44	11.649%	$182.4791	$182.48	$182.50	$182.50
Purchase #2	$33.73	9.741%	$37.0156	$37.02	$37.00	$37.00
Purchase #3	$154.66	5.216%	$162.7271	$162.73	$162.75	$162.70
Purchase #4	$179.60	9.392%	$196.468	$196.47	$196.45	$196.50
Purchase #5	$137.58	7.618%	$148.0608	$148.06	$148.05	$148.10
Purchase #6	$164.70	11.741%	$184.0374	$184.04	$184.05	$184.00
Purchase #7	$182.53	7.811%	$196.7874	$196.79	$196.80	$196.80
7 purchase totals =	$1,016.24		$1,107.5754	$1,107.59	$1,107.60	$1,107.60