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	$228.80	3.715%	$237.2999	$237.30	$237.30	$237.30
Purchase #2	$70.66	9.737%	$77.5402	$77.54	$77.55	$77.50
Purchase #3	$86.79	4.152%	$90.3935	$90.39	$90.40	$90.40
Purchase #4	$150.73	11.419%	$167.9419	$167.94	$167.95	$167.90
Purchase #5	$94.82	4.227%	$98.828	$98.83	$98.85	$98.80
Purchase #6	$85.97	7.860%	$92.7272	$92.73	$92.75	$92.70
Purchase #7	$234.71	8.704%	$255.1392	$255.14	$255.15	$255.10
7 purchase totals =	$952.48		$1,019.8699	$1,019.87	$1,019.95	$1,019.70