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	$140.33	13.740%	$159.6113	$159.61	$159.60	$159.60
Purchase #2	$137.34	13.601%	$156.0196	$156.02	$156.00	$156.00
Purchase #3	$210.83	13.444%	$239.174	$239.17	$239.15	$239.20
Purchase #4	$199.51	9.230%	$217.9248	$217.92	$217.90	$217.90
Purchase #5	$115.30	11.673%	$128.759	$128.76	$128.75	$128.80
Purchase #6	$108.62	3.621%	$112.5531	$112.55	$112.55	$112.60
Purchase #7	$43.61	3.472%	$45.1241	$45.12	$45.10	$45.10
7 purchase totals =	$955.54		$1,059.1659	$1,059.15	$1,059.05	$1,059.20