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	$208.61	7.331%	$223.9032	$223.90	$223.90	$223.90
Purchase #2	$135.42	5.421%	$142.7611	$142.76	$142.75	$142.80
Purchase #3	$59.36	5.305%	$62.509	$62.51	$62.50	$62.50
Purchase #4	$34.83	4.757%	$36.4869	$36.49	$36.50	$36.50
Purchase #5	$128.81	12.778%	$145.2693	$145.27	$145.25	$145.30
Purchase #6	$190.55	12.333%	$214.0505	$214.05	$214.05	$214.10
Purchase #7	$91.97	13.696%	$104.5662	$104.57	$104.55	$104.60
7 purchase totals =	$849.55		$929.5462	$929.55	$929.50	$929.70