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	$67.68	10.571%	$74.8345	$74.83	$74.85	$74.80
Purchase #2	$147.84	13.231%	$167.4007	$167.40	$167.40	$167.40
Purchase #3	$111.33	11.134%	$123.7255	$123.73	$123.75	$123.70
Purchase #4	$201.59	11.572%	$224.918	$224.92	$224.90	$224.90
Purchase #5	$33.67	13.609%	$38.2522	$38.25	$38.25	$38.30
Purchase #6	$168.51	10.233%	$185.7536	$185.75	$185.75	$185.80
Purchase #7	$109.73	7.365%	$117.8116	$117.81	$117.80	$117.80
7 purchase totals =	$840.35		$932.6961	$932.69	$932.70	$932.70