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	$234.76	8.550%	$254.832	$254.83	$254.85	$254.80
Purchase #2	$62.33	4.843%	$65.3486	$65.35	$65.35	$65.30
Purchase #3	$171.68	8.266%	$185.8711	$185.87	$185.85	$185.90
Purchase #4	$238.46	10.195%	$262.771	$262.77	$262.75	$262.80
Purchase #5	$149.88	12.426%	$168.5041	$168.50	$168.50	$168.50
Purchase #6	$196.94	13.109%	$222.7569	$222.76	$222.75	$222.80
Purchase #7	$171.65	11.774%	$191.8601	$191.86	$191.85	$191.90
7 purchase totals =	$1,225.70		$1,351.9438	$1,351.94	$1,351.90	$1,352.00