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	$102.90	13.217%	$116.5003	$116.50	$116.50	$116.50
Purchase #2	$167.75	7.144%	$179.7341	$179.73	$179.75	$179.70
Purchase #3	$141.26	12.860%	$159.426	$159.43	$159.45	$159.40
Purchase #4	$92.85	13.247%	$105.1498	$105.15	$105.15	$105.10
Purchase #5	$178.59	11.688%	$199.4636	$199.46	$199.45	$199.50
Purchase #6	$158.32	10.616%	$175.1273	$175.13	$175.15	$175.10
Purchase #7	$180.69	8.744%	$196.4895	$196.49	$196.50	$196.50
7 purchase totals =	$1,022.36		$1,131.8906	$1,131.89	$1,131.95	$1,131.80