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	$179.36	3.871%	$186.303	$186.30	$186.30	$186.30
Purchase #2	$148.81	12.428%	$167.3041	$167.30	$167.30	$167.30
Purchase #3	$33.64	11.156%	$37.3929	$37.39	$37.40	$37.40
Purchase #4	$164.39	3.365%	$169.9217	$169.92	$169.90	$169.90
Purchase #5	$99.38	8.262%	$107.5908	$107.59	$107.60	$107.60
Purchase #6	$205.63	6.779%	$219.5697	$219.57	$219.55	$219.60
Purchase #7	$38.57	11.250%	$42.9091	$42.91	$42.90	$42.90
7 purchase totals =	$869.78		$930.9913	$930.98	$930.95	$931.00