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	$34.54	10.482%	$38.1605	$38.16	$38.15	$38.20
Purchase #2	$13.65	9.523%	$14.9499	$14.95	$14.95	$14.90
Purchase #3	$76.98	11.299%	$85.678	$85.68	$85.70	$85.70
Purchase #4	$152.51	6.486%	$162.4018	$162.40	$162.40	$162.40
Purchase #5	$64.75	11.793%	$72.386	$72.39	$72.40	$72.40
Purchase #6	$220.86	13.592%	$250.8793	$250.88	$250.90	$250.90
Purchase #7	$78.84	8.227%	$85.3262	$85.33	$85.35	$85.30
7 purchase totals =	$642.13		$709.7817	$709.79	$709.85	$709.80