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	$146.96	11.685%	$164.1323	$164.13	$164.15	$164.10
Purchase #2	$172.89	3.684%	$179.2593	$179.26	$179.25	$179.30
Purchase #3	$78.39	5.127%	$82.4091	$82.41	$82.40	$82.40
Purchase #4	$137.61	3.870%	$142.9355	$142.94	$142.95	$142.90
Purchase #5	$102.81	4.242%	$107.1712	$107.17	$107.15	$107.20
Purchase #6	$211.36	4.636%	$221.1586	$221.16	$221.15	$221.20
Purchase #7	$34.75	13.364%	$39.394	$39.39	$39.40	$39.40
7 purchase totals =	$884.77		$936.4600	$936.46	$936.45	$936.50