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	$235.35	7.624%	$253.2931	$253.29	$253.30	$253.30
Purchase #2	$124.62	10.189%	$137.3175	$137.32	$137.30	$137.30
Purchase #3	$166.87	9.622%	$182.9262	$182.93	$182.95	$182.90
Purchase #4	$53.28	11.357%	$59.331	$59.33	$59.35	$59.30
Purchase #5	$124.56	13.121%	$140.9035	$140.90	$140.90	$140.90
Purchase #6	$159.89	5.428%	$168.5688	$168.57	$168.55	$168.60
Purchase #7	$102.99	11.144%	$114.4672	$114.47	$114.45	$114.50
7 purchase totals =	$967.56		$1,056.8073	$1,056.81	$1,056.80	$1,056.80