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	$212.48	13.428%	$241.0118	$241.01	$241.00	$241.00
Purchase #2	$96.49	13.700%	$109.7091	$109.71	$109.70	$109.70
Purchase #3	$48.41	6.824%	$51.7135	$51.71	$51.70	$51.70
Purchase #4	$234.51	13.783%	$266.8325	$266.83	$266.85	$266.80
Purchase #5	$143.39	9.183%	$156.5575	$156.56	$156.55	$156.60
Purchase #6	$106.82	4.232%	$111.3406	$111.34	$111.35	$111.30
Purchase #7	$168.85	13.534%	$191.7022	$191.70	$191.70	$191.70
7 purchase totals =	$1,010.95		$1,128.8672	$1,128.86	$1,128.85	$1,128.80