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	$115.37	13.617%	$131.0799	$131.08	$131.10	$131.10
Purchase #2	$56.51	6.356%	$60.1018	$60.10	$60.10	$60.10
Purchase #3	$125.83	5.385%	$132.6059	$132.61	$132.60	$132.60
Purchase #4	$193.74	5.435%	$204.2698	$204.27	$204.25	$204.30
Purchase #5	$90.57	9.801%	$99.4468	$99.45	$99.45	$99.40
Purchase #6	$155.71	11.165%	$173.095	$173.10	$173.10	$173.10
Purchase #7	$184.60	10.436%	$203.8649	$203.86	$203.85	$203.90
7 purchase totals =	$922.33		$1,004.4641	$1,004.47	$1,004.45	$1,004.50