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	$47.69	6.170%	$50.6325	$50.63	$50.65	$50.60
Purchase #2	$127.40	3.688%	$132.0985	$132.10	$132.10	$132.10
Purchase #3	$28.74	7.748%	$30.9668	$30.97	$30.95	$31.00
Purchase #4	$239.39	6.636%	$255.2759	$255.28	$255.30	$255.30
Purchase #5	$167.34	10.798%	$185.4094	$185.41	$185.40	$185.40
Purchase #6	$196.79	13.205%	$222.7761	$222.78	$222.80	$222.80
Purchase #7	$90.58	6.371%	$96.3509	$96.35	$96.35	$96.40
7 purchase totals =	$897.93		$973.5101	$973.52	$973.55	$973.60