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	$140.91	13.525%	$159.9681	$159.97	$159.95	$160.00
Purchase #2	$69.90	8.848%	$76.0848	$76.08	$76.10	$76.10
Purchase #3	$182.59	4.196%	$190.2515	$190.25	$190.25	$190.30
Purchase #4	$157.32	13.199%	$178.0847	$178.08	$178.10	$178.10
Purchase #5	$206.73	8.293%	$223.8741	$223.87	$223.85	$223.90
Purchase #6	$235.85	11.317%	$262.5411	$262.54	$262.55	$262.50
Purchase #7	$134.43	10.121%	$148.0357	$148.04	$148.05	$148.00
7 purchase totals =	$1,127.73		$1,238.8400	$1,238.83	$1,238.85	$1,238.90