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	$57.90	13.373%	$65.643	$65.64	$65.65	$65.60
Purchase #2	$125.83	13.369%	$142.6522	$142.65	$142.65	$142.70
Purchase #3	$80.91	6.155%	$85.89	$85.89	$85.90	$85.90
Purchase #4	$105.52	4.741%	$110.5227	$110.52	$110.50	$110.50
Purchase #5	$75.92	10.176%	$83.6456	$83.65	$83.65	$83.60
Purchase #6	$102.96	3.454%	$106.5162	$106.52	$106.50	$106.50
Purchase #7	$109.61	4.627%	$114.6817	$114.68	$114.70	$114.70
7 purchase totals =	$658.65		$709.5514	$709.55	$709.55	$709.50