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	$133.77	6.727%	$142.7687	$142.77	$142.75	$142.80
Purchase #2	$140.72	11.773%	$157.287	$157.29	$157.30	$157.30
Purchase #3	$7.38	3.397%	$7.6307	$7.63	$7.65	$7.60
Purchase #4	$240.38	12.589%	$270.6414	$270.64	$270.65	$270.60
Purchase #5	$172.77	12.622%	$194.577	$194.58	$194.60	$194.60
Purchase #6	$179.40	4.254%	$187.0317	$187.03	$187.05	$187.00
Purchase #7	$42.32	7.430%	$45.4644	$45.46	$45.45	$45.50
7 purchase totals =	$916.74		$1,005.4009	$1,005.40	$1,005.45	$1,005.40