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	$216.95	3.212%	$223.9184	$223.92	$223.90	$223.90
Purchase #2	$149.93	9.288%	$163.8555	$163.86	$163.85	$163.90
Purchase #3	$129.92	12.419%	$146.0548	$146.05	$146.05	$146.10
Purchase #4	$209.76	6.549%	$223.4972	$223.50	$223.50	$223.50
Purchase #5	$57.80	3.416%	$59.7744	$59.77	$59.75	$59.80
Purchase #6	$174.78	6.816%	$186.693	$186.69	$186.70	$186.70
Purchase #7	$59.63	5.168%	$62.7117	$62.71	$62.70	$62.70
7 purchase totals =	$998.77		$1,066.5050	$1,066.50	$1,066.45	$1,066.60